SetOututFileHandle to work with IOBase.
I did make one change after checking with Larry --
I renamed SBDebugger::Flush to FlushDebuggerOutputHandles
and added a short docstring to the .i file to make it
a little clearer under which context programs may need
to use this API.
Differential Revision: https://reviews.llvm.org/D39128
<rdar://problem/34870417>
llvm-svn: 317182