Huge performance bottleneck with cin.read.

[Benjamin Kosnik]

looks like the only performance hit is on cin/cout/cerr. This is to be 
expected: they are no longer buffered. I'm just relieved that normal 
string/file streams are ok, which is cool. I would actually expect 
stringstreams to be faster than the old memory-based stream implementation.

One way around this is to acually use sync_with_stdio, providing this was 
working. I'm working on that now.

-benjamin