PR libstdc++/26211 + N3168

2010-11-18  Paolo Carlini  <paolo.carlini@oracle.com>

	PR libstdc++/26211 + N3168
	* include/bits/istream.tcc (basic_istream<>::tellg, seekg(pos_type),
	seekg(off_type, ios_base::seekdir)): Construct a sentry.
	(basic_istream<>::tellg, seekg(pos_type), seekg(off_type,
	ios_base::seekdir, putback, unget)): Clear eofbit first, per N3168.  
	* testsuite/27_io/basic_istream/seekg/char/26211.cc: New.
	* testsuite/27_io/basic_istream/seekg/wchar_t/26211.cc: Likewise.
	* testsuite/27_io/basic_istream/tellg/char/26211.cc: Likewise.
	* testsuite/27_io/basic_istream/tellg/wchar_t/26211.cc: Likewise.
	* testsuite/27_io/basic_istream/tellg/char/8348.cc: Tweak.
	* testsuite/27_io/basic_istream/tellg/wchar_t/8348.cc: Likewise.

From-SVN: r166911