Use gdb::function_view in iterate_over_symtabs & co
    
    I wanted to pass a lambda to iterate_over_symtabs (see following
    patch), so I converted it to function_view, and then the rest is
    cascaded from that.
    
    This gets rid of a bunch of single-use callback functions and
    corresponding manually managed callback capture types
    (add_partial_datum, search_symbols_data, etc.) in favor of letting the
    compiler generate them for us by using lambdas with a capture.  In a
    couple cases, it was more natural to convert the existing function
    callbacks to function objects (i.e., operator(), e.g.,
    decode_compound_collector).
    
    gdb/ChangeLog:
    2017-02-23  Pedro Alves  <palves@redhat.com>
    
    	* ada-lang.c: Include "common/function-view.h".
    	(ada_iterate_over_symbols): Adjust to use function_view as
    	callback type.
    	(struct add_partial_datum, ada_complete_symbol_matcher): Delete.
    	(ada_make_symbol_completion_list): Use a lambda.
    	(ada_exc_search_name_matches): Delete.
    	(name_matches_regex): New.
    	(ada_add_global_exceptions): Use a lambda and name_matches_regex.
    	* compile/compile-c-support.c: Include "common/function-view.h".
    	(print_one_macro): Change prototype to accept a ui_file pointer.
    	(write_macro_definitions): Use a lambda.
    	* dwarf2read.c: Include "common/function-view.h".
    	(dw2_map_expand_apply, dw2_map_symtabs_matching_filename)
    	(dw2_expand_symtabs_matching): Adjust to use function_view as
    	callback type.
    	* language.h: Include "common/function-view.h".
    	(struct language_defn) <la_iterate_over_symbols>: Adjust to use
    	function_view as callback type.
    	(LA_ITERATE_OVER_SYMBOLS): Remove DATA parameter.
    	* linespec.c: Include "common/function-view.h".
    	(collect_info::add_symbol): New method.
    	(struct symbol_and_data_callback, iterate_inline_only, struct
    	symbol_matcher_data, iterate_name_matcher): Delete.
    	(iterate_over_all_matching_symtabs): Adjust to use function_view
    	as callback type and lambdas.
    	(iterate_over_file_blocks): Adjust to use function_view as
    	callback type.
    	(decode_compound_collector): Now a class with private fields.
    	(decode_compound_collector::release_symbols): New method.
    	(collect_one_symbol): Rename to...
    	(decode_compound_collector::operator()): ... this and adjust.
    	(lookup_prefix_sym): decode_compound_collector construction bits
    	move to decode_compound_collector ctor.  Pass the
    	decode_compound_collector object directly as callback.  Remove
    	cleanups and use decode_compound_collector::release_symbols
    	instead.
    	(symtab_collector): Now a class with private fields.
    	(symtab_collector::release_symtabs): New method.
    	(add_symtabs_to_list): Rename to...
    	(symtab_collector::operator()): ... this and adjust.
    	(collect_symtabs_from_filename): symtab_collector construction
    	bits move to symtab_collector ctor.  Pass the symtab_collector
    	object directly as callback.  Remove cleanups and use
    	symtab_collector::release_symtabs instead.
    	(collect_symbols): Delete.
    	(add_matching_symbols_to_info): Use lambdas.
    	* macrocmd.c (print_macro_callback): Delete.
    	(info_macro_command): Use a lambda.
    	(info_macros_command): Pass print_macro_definition as callable
    	directly.
    	(print_one_macro): Remove 'ignore' parameter.
    	(macro_list_command): Adjust.
    	* macrotab.c (macro_for_each_data::fn): Now a function_view.
    	(macro_for_each_data::user_data): Delete field.
    	(foreach_macro): Adjust to call the function_view.
    	(macro_for_each): Adjust to use function_view as callback type.
    	(foreach_macro_in_scope): Adjust to call the function_view.
    	(macro_for_each_in_scope): Adjust to use function_view as callback
    	type.
    	* macrotab.h: Include "common/function-view.h".
    	(macro_callback_fn): Declare a prototype instead of a pointer.
    	Remove "user_data" parameter.
    	(macro_for_each, macro_for_each_in_scope): Adjust to use
    	function_view as callback type.
    	* psymtab.c (partial_map_expand_apply)
    	(psym_map_symtabs_matching_filename, recursively_search_psymtabs):
    	Adjust to use function_view as callback type and to return bool.
    	(psym_expand_symtabs_matching): Adjust to use function_view as
    	callback types.
    	* symfile-debug.c (debug_qf_map_symtabs_matching_filename): Adjust
    	to use function_view as callback type and to return bool.
    	(debug_qf_expand_symtabs_matching): Adjust to use function_view as
    	callback types.
    	* symfile.c (expand_symtabs_matching): Adjust to use function_view
    	as callback types.
    	* symfile.h: Include "common/function-view.h".
    	(expand_symtabs_file_matcher_ftype)
    	(expand_symtabs_symbol_matcher_ftype)
    	(expand_symtabs_exp_notify_ftype): Remove "data" parameter and
    	return bool.
    	(quick_symbol_functions::map_symtabs_matching_filename)
    	(quick_symbol_functions::expand_symtabs_matching): Adjust to use
    	function_view as callback type and return bool.
    	(expand_symtabs_matching): Adjust to use function_view as callback
    	type.
    	(maintenance_expand_name_matcher)
    	(maintenance_expand_file_matcher): Delete.
    	(maintenance_expand_symtabs): Use lambdas.
    	* symtab.c (iterate_over_some_symtabs): Adjust to use
    	function_view as callback types and return bool.
    	(iterate_over_symtabs): Likewise.  Use unique_xmalloc_ptr instead
    	of a cleanup.
    	(lookup_symtab_callback): Delete.
    	(lookup_symtab): Use a lambda.
    	(iterate_over_symbols): Adjust to use function_view as callback
    	type.
    	(struct search_symbols_data, search_symbols_file_matches)
    	(search_symbols_name_matches): Delete.
    	(search_symbols): Use a pair of lambdas.
    	(struct add_name_data, add_macro_name, symbol_completion_matcher)
    	(symtab_expansion_callback): Delete.
    	(default_make_symbol_completion_list_break_on_1): Use lambdas.
    	* symtab.h: Include "common/function-view.h".
    	(iterate_over_some_symtabs): Adjust to use function_view as
    	callback type and return bool.
    	(iterate_over_symtabs): Adjust to use function_view as callback
    	type.
    	(symbol_found_callback_ftype): Remove 'data' parameter and return
    	bool.
    	(iterate_over_symbols): Adjust to use function_view as callback
    	type.