*** Major changes in libio version 0.63 (released with libg++ 2.5.3):

* There is a g++ bug that causes inconsistent name mangling for the
assembler name of the virtual function table for the istream class.
A work-around has been put into streambuf.h, which will make g++
always do the right thing.  Note that this may require you to
recompile programs that were incorrectly compiled by g++.

* Functions that do printf-style formatting to the unbuffered
streams have been optimized to write to a temporary buffer.