objcopy bfd_map_over_sections and global status

This patch started life as a relatively simple change to fix some
unimportant objcopy memory leaks, but expanded into a larger patch
when I was annoyed by the awkwardness of passing data when using
bfd_map_over_sections.  A simple loop over sections is much more
convenient, and we really don't need the abstraction layer.  Sections
in a list isn't going to disappear any time soon.

The patch also removes use of the global "status" variable by all but
the top-level functions called from main.

	* objcopy.c (filter_symbols): Return success as a bool.  Pass
	symcount as a pointer, updated on return.
	(merge_gnu_build_notes): Similarly return a bool and add newsize
	param with updated smaller section size.
	(setup_bfd_headers): Return bool success rather than setting
	"status" on failure.
	(setup_section): Likewise.
	(copy_relocations_in_section, copy_section): Likewise, and adjust
	params.
	(mark_symbols_used_in_relocations): Likewise, and free memory
	on failure path.  Don't call bfd_fatal.
	(get_sections): Delete function.
	(copy_object): Don't use bfd_map_over_sections, instead use a
	loop allowing easy detection of failure status.  Free memory on
	error paths.
	(copy_archive): Return bool success rather than setting "status"
	on failure.
	(copy_file): Set "status" here.
	* testsuite/binutils-all/strip-13.d: Adjust to suit.