objcopy: Add --update-section option.

objcopy: Add --update-section option.

New option for objcopy --update-section allows the contents of a section
to be updated while maintaining the section flags, and, for ELF files,
the section to segment mapping.

New test uses --dump-section and --update-section to check that a
section can be made larger and smaller with an update.

binutils/ChangeLog:

	* objcopy.c (update_sections): New list.
	(command_line_switch): Add OPTION_UPDATE_SECTION.
	(copy_options): Add update-section.
	(copy_usage): Document new option.
	(is_update_section): New function.
	(is_strip_section_1): Add check for attempt to update and remove
	the same section.
	(copy_object): Update size and content of requested sections.
	(skip_section): Don't copy for updated sections.
	(copy_main): Handle --update-section.
	* doc/binutils.texi (objcopy): Add description of --update-section
	option.
	* NEWS: Mention --update-section option.

binutils/testsuite/ChangeLog:

	* binutils-all/update-1.s: New file.
	* binutils-all/update-2.s: New file.
	* binutils-all/update-3.s: New file.
	* binutils-all/update-4.s: New file.
	* binutils-all/update-section.exp: New file.