[Patch] Fix libstdc++/9182

[Benjamin Kosnik]

2003-03-02  Paolo Carlini  <pcarlini@unitus.it>

	PR libstdc++/9182
	* include/bits/fstream.tcc (_M_really_overflow): Check
	for _M_convert_to_external possible failures.
	* include/std/std_fstream.h (sync): Check _M_really_overflow
	return value and return -1 in case of failure.
	* testsuite/27_io/filebuf_virtuals.cc (test13, test14): Add.

	* include/bits/fstream.tcc (_M_convert_to_external):
	Set __elen to zero if codecvt::out eventually fails.

This looks good, thanks. Please put it in everywhere.

As you both probably noted, error correction for filebuf and codecvt was
very sketchy. This improves things, thanks!

-benjamin