* testsuite/testsuite_hooks.cc (try_mkfifo): Remove.
	* testsuite/testsuite_hooks.h (try_mkfifo): Likewise.
	* testsuite/27_io/basic_filebuf/close/char/4879.cc: Use
	dg-require-fork and dg-require-mkfifo.  Replace try_mkfifo with
	mkfifo.
	* testsuite/27_io/basic_filebuf/close/char/9964.cc: Likewise.
	* testsuite/27_io/basic_filebuf/imbue/char/13171-2.cc: Likewise.
	* testsuite/27_io/basic_filebuf/imbue/char/13582-2.cc: Likewise.
	* testsuite/27_io/basic_filebuf/imbue/wchar_t/13582-2.cc:
	Likewise.
	* testsuite/27_io/basic_filebuf/imbue/wchar_t/14975-2.cc:
	Likewise.
	* testsuite/27_io/basic_filebuf/open/char/9507.cc: Likewise.
	* testsuite/27_io/basic_filebuf/showmanyc/char/9533-1.cc:
	Likewise.
	* testsuite/27_io/basic_filebuf/underflow/char/10097.cc: Likewise.
	* testsuite/27_io/objects/char/7.cc: Likewise.
	* testsuite/27_io/objects/char/9661-1.cc: Likewise.
	* testsuite/27_io/objects/wchar_t/7.cc: Likewise.
	* testsuite/27_io/objects/wchar_t/9661-1.cc: Likewise.

	* lib/target-supports-dg.exp (dg-require-fork): New function.
	(dg-require-mkfifo): Likewise.
	* lib/target-supports.exp (check_function_available): New
	function.
	(check_fork_available): Likewise.
	(check_mkfifo_available): Likewise.

From-SVN: r99325