New gold linker option -z,text-unlikely-segment.

New gold linker option -z,text-unlikely-segment.

2017-10-04  Sriraman Tallam  <tmsriram@google.com>

	* options.h (-z,text_unlikely_segment): New option.
	* layout.cc (Layout::layout): Create new output section
	for .text.unlikely sections with the new option.
	(Layout::segment_precedes): Check for the new option
	when segment flags match.
	* testsuite/text_unlikely_segment.cc: New test source.
	* testsuite/text_unlikely_segment.sh: New test script.
	* testsuite/Makefile.am (text_unlikely_segment): New test.
	* testsuite/Makefile.in: Regenerate.