Reset x86 Linux targets to not compressing debug sections by default.  Enable compression of debug sections by default in the linker, if so configured.

	PR gas/19109
.	* configure.ac: Note the 'none' is an acceptable argument to
	--enable-compressed-debug-sections.
	* configure: Regenerate.

gas	* configure.ac: Restore --enable-compressed-debug-sections.
	Do not enable compressed debug sections by default for x86 Linux
	targets.
	* configure: Regenerate.

ld	* configure.ac: Add --enable-compressed-debug-sections.
	* configure: Regenerate.
	* config.in: Regenerate.
	* ld.texinfo: Document how to determine the default action for
	debug sections.
	* ldmain.c (main): If DEFAULT_FLAG_COMPRESS_DEBUG is defined then
	set the compress_debug field of the link_info structure to
	zlib-gabi.
	* lexsup.c (elf_static_list_options): Output the default setting
	for the --compress-debug-sections option.
	* NEWS: Mention the new configure option.