Add note merging to strip and add code to merge stack size notes.

Add note merging to strip and add code to merge stack size notes.

	* objcopy.c: Add --no-merge-notes option to disable note merging.
	Add --[no-]merge-notes option to strip, and enable it by default.
	(num_bytes): New function.
	(merge_gnu_build_notes): Add code to merge stack size notes.
	* binutils.texi: Update strip and objcopy documentation.
	* readelf.c (print_gnu_build_attribute_name): Use defined
	constants for note types.