testsuite: Cut down 27_io/basic_istream/.../94749.cc for simulators

The test wchar_t/94749.cc can take about 10 minutes on some
simulator/host combinations with char/94749.cc at a third of
that time.  The cause is test05 which is quite heavy and
includes wrapping a 32-bit counter.  Run it only for native
setups.

	* testsuite/27_io/basic_istream/ignore/wchar_t/94749.cc (main)
	[! SIMULATOR_TEST]: Also exclude running test05.
	* testsuite/27_io/basic_istream/ignore/char/94749.cc: Ditto.