Add reverseColor to raw_ostream.

To be used in printing unprintable source in clang diagnostics.
Patch by Seth Cantrell!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154800 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/Unix/Process.inc

@@ -290,6 +290,10 @@ const char *Process::OutputBold(bool bg) {
   return "\033[1m";
 }
 
+const char *Process::OutputReverse() {
+  return "\033[7m";
+}
+
 const char *Process::ResetColor() {
   return "\033[0m";
 }