Add support for writing through StreamInterface.

This adds method and tests for writing to a PDB stream.  With
this, even a PDB stream which is discontiguous can be treated
as a sequential stream of bytes for the purposes of writing.

Reviewed By: ruiu
Differential Revision: http://reviews.llvm.org/D21157

llvm-svn: 272369
diff --git a/llvm/lib/DebugInfo/CodeView/CMakeLists.txt b/llvm/lib/DebugInfo/CodeView/CMakeLists.txt
index 6c4e09f..4393f9c 100644
--- a/llvm/lib/DebugInfo/CodeView/CMakeLists.txt
+++ b/llvm/lib/DebugInfo/CodeView/CMakeLists.txt
@@ -11,6 +11,7 @@
   ModuleSubstreamVisitor.cpp
   RecordSerialization.cpp
   StreamReader.cpp
+  StreamWriter.cpp
   SymbolDumper.cpp
   TypeDumper.cpp
   TypeRecord.cpp