* linkage.m4 (GLIBCXX_CHECK_STDLIB_DECL_AND_LINKAGE): New.
	(GLIBCXX_CHECK_STDLIB_SUPPORT): Check for atexit and at_quick_exit.
	* include/c_std/cstdlib: Add atexit and at_quick_exit.
	* include/c_global/cstdlib: Add atexit and at_quick_exit.
	* testsuite/18_support/quick_exit/quick_exit.cc: New.

From-SVN: r195948