Overloaded __pad_and_output on ostreambuf_iterator and in this overload call...

Overloaded __pad_and_output on ostreambuf_iterator and in this overload call sputn instead of dereferencing the iterator which calls sputc.  This is intended to be purely a performance optimization, especially for clients who may have overloaded the virtual function xsputn.

llvm-svn: 164241