Use raw_ostream in TypePrinter and eliminate uses of temporary std::strings.

Part of rdar://10796159

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156228 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index fcde542..afc7410 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -414,9 +414,7 @@
     if (FT) {
       for (unsigned i = 0, e = Decl->getNumParams(); i != e; ++i) {
         if (i) POut << ", ";
-        std::string Param;
-        Decl->getParamDecl(i)->getType().getAsStringInternal(Param, Policy);
-        POut << Param;
+        POut << Decl->getParamDecl(i)->getType().stream(Policy);
       }
 
       if (FT->isVariadic()) {