[Patch] Fix filebuf_virtuals.cc for unsigned char platforms

[Paolo Carlini]

Hi,

currently this test is failing on mips, arm and powerpc: all
unsigned char platforms. Honestly, I'm not 100% sure but the
testcase I blindly copied from libstdc++/9538 seems weak wrt
char signedness.

Kaveh, Jeroen, Mark, could you possibly test the below on your
favourite unsigned char platform and report?

Thanks!

Paolo.

///////////
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: CL_signedness
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20030206/36d327f0/attachment.ksh>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: patch_signedness
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20030206/36d327f0/attachment-0001.ksh>