Fix PR 17704.

Fix PR 17704.

This fix keeps the section with the highest alignment when folding sections with ICF.

	PR gold/17704
	* icf.cc (match_sections): Add new parameter section_addraligns.
	Check section alignment and keep the section with the strictest
	alignment.
	(find_identical_sections): New local variable section_addraligns.
	Store each section's alignment.
	* testsuite/pr17704a_test.s: New file.
	* testsuite/Makefile.am (pr17704a_test): New test.
	* testsuite/Makefile.in: Regenerate.