[Patch] Fix libstdc++/9424

[Benjamin Kosnik]

2003-02-27  Paolo Carlini <pcarlini@unitus.it>
	    Petur Runolfsson  <peturr02@ru.is>

	PR libstdc++/9424
	* include/bits/streambuf.tcc (__copy_streambufs): Use
	sgetn-sputn only when sputn cannot fail, otherwise fall back
	to safe snextc-sputc.
	* testsuite/27_io/streambuf_members.cc (test11, test12): Add.

Looks good y'all.

Yes, __copy_streambufs is getting a bit unweidly. I think that all the
special-casing for interactivity is a kludge, in general. A temporary
evil, since this is being worked on separately. Eventually, this will be
able to be simpler.

Till then, this is fine.

-benjamin