Emit a note warning the user that creating an executable stack because of a...

Emit a note warning the user that creating an executable stack because of a missing .note.GNU-stack section is deprecated.

	PR 29072
bfd	* elflink.c (bfd_elf_size_dynamic_sections): Display a note to the
	user that the current ehaviour of creating an executable stack
	because of a missing .note.GNU-stack section is deprecated and
	will be changed in a future release.

binutils* testsuite/lib/binutils-common.exp (prune_warnings_extra): Filter
	out notes about the executable stacjk behaviour beign deprecated.

ld	* testsuite/ld-elf/pr29072.b.warn: Update to include the note
	about the linker's behaviour being depreccated.