Avoid using size_t to get DWARF data
    
    This can cause issues on i686 compared to x86_64 as size_t has
    different size on these two platforms.  Rather, use int64_t which has
    the same fixed size on both platforms.
    
    	* src/abg-dwarf-reader.cc (die_size_in_bits, die_location_expr):
    	Take uint64_t rather than size_t and adjust.
    	(expr_result::const_value_): Make this be int64_t rather than
    	ssize_t.
    	(expr_result::expr_result): Take int64_t rather than ssize_t.
    	(expr_result::const_value): Return int64_t rather than ssize_t.
    	(expr_result::{operator(), operator=, operator+=}): Make these
    	operators return or take int64_t.
    	too.
    	(op_pushes_constant_value, op_manipulates_stack)
    	(op_is_arith_logic, op_is_control_flow)
    	(eval_last_constant_dwarf_sub_expr, die_member_offset)
    	(die_virtual_function_index): Take
    	uint64_t rather than size_t, or int64_t rather than ssize_t.
    	(finish_member_function_reading, build_class_type_and_add_to_ir)
    	(build_union_type_and_add_to_ir): Adjust.
    
    Signed-off-by: Dodji Seketeli <dodji@redhat.com>