[PATCH] Update links to libstdc++ Doxygen pages

[Jonathan Wakely <jwakely at redhat dot com>]

There's no reason to have a fixed list of release versions in the
libstdc++ docs which needs updating manually. The page at
https://gcc.gnu.org/onlinedocs already links to the Doxygen docs for
each release, so we can just refer to that.

	* doc/xml/api.xml: Replace hardcoded links for specific versions with
	link to docs for all releases.
	* doc/html/*: Regenerate.

Committed to trunk. I'll probably backport this to gcc-5 and gcc-6,
because the list of releases on those branches haven't been updated to
refer to anything later than 4.9.2

Attachment: patch.txt
Description: Text document