* doc/xml/manual/abi.xml: Document header locations in recent
	releases.
	* doc/xml/manual/evolution.xml: Add API changes since GCC 5.
	* doc/xml/manual/spine.xml: Update copyright years.
	* doc/xml/manual/strings.xml: Adjust tolower example to avoid
	undefined behaviour.
	* doc/xml/manual/test.xml: Update outdated notes on VERIFY in tests.
	* doc/html/*: Regenerate.

From-SVN: r259308