libstdc++/4150: catastrophic performance decrease in C++ code

[Jason Merrill]

>>>>> "Benjamin" == Benjamin Kosnik <bkoz@redhat.com> writes:

>> Only the concern I have is about the remaining failing interactive
>> test case.  

> ...it was disabled because I don't think it ever worked.

Which seems like a significant bug to me.  This seems to be the purpose of
the _IO_LINE_BUF code in libio.  I suppose for the time being we could just
do unbuffered i/o on tty's.

Jason