* doc/doxygen/user.cfg.in: Set __cplusplus to 201103L. Change to
_GLIBCXX_INCLUDE_AS_CXX11. DIRECTORY_GRAPH, MARKDOWN_SUPPORT,
AUTOLINK_SUPPORT to NO. Update to doxygen 1.8.3.1.
* include/bits/stl_pair.h: Add to utilities group.
* include/std/tuple: Same.
* include/std/typeindex: Same.