Add dwarf2_per_objfile parameters to dwarf2_fetch_* functions
    
    This allows removing dwarf2_per_cu_data references.
    
    gdb/ChangeLog:
    
    	* dwarf2/read.h (dwarf2_fetch_die_loc_sect_off,
    	dwarf2_fetch_die_loc_cu_off, dwarf2_fetch_constant_bytes,
    	dwarf2_fetch_die_type_sect_off): Add dwarf2_per_objfile
    	parameter.
    	* dwarf2/read.c (dwarf2_fetch_die_loc_sect_off,
    	dwarf2_fetch_die_loc_cu_off, dwarf2_fetch_constant_bytes,
    	dwarf2_fetch_die_type_sect_off): Add dwarf2_per_objfile
    	parameter.
    	* dwarf2/loc.c (indirect_synthetic_pointer, per_cu_dwarf_call,
    	sect_variable_value): Add dwarf2_per_objfile parameter.
    	(class dwarf_evaluate_loc_desc) 
    	dwarf_variable_value>: Update.
    	(fetch_const_value_from_synthetic_pointer): Add
    	dwarf2_per_objfile parameter.
    	(fetch_const_value_from_synthetic_pointer): Update.
    	(coerced_pieced_ref): Update.
    	(class symbol_needs_eval_context) 
    	dwarf_variable_value>: Update.
    	(dwarf2_compile_expr_to_ax): Update.