Fixes to Doxygen comments in libstdc++ headers

Fixes to Doxygen comments in libstdc++ headers

	* include/bits/refwrap.h: Fix Doxygen warning.
	* include/bits/specfun.h: Likewise.
	* include/bits/std_function.h: Likewise.
	* include/bits/stl_algo.h (set_union, set_intersection)
	(set_difference, set_symmetric_difference): Add Doxygen @param tags
	for output iterator parameters.
	* include/bits/stl_iterator.h (inserter): Add Doxygen @param tag for
	iterator parameter.
	* include/std/mutex (try_lock, lock): Change Mutex to Lockable in
	Doxygen comments.

From-SVN: r248160