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

include/llvm/Support/Process.h

@@ -136,6 +136,10 @@ namespace sys {
       /// Same as OutputColor, but only enables the bold attribute.
       static const char *OutputBold(bool bg);
 
+      /// This function returns the escape sequence to reverse forground and
+      /// background colors.
+      static const char *OutputReverse();
+
       /// Resets the terminals colors, or returns an escape sequence to do so.
       static const char *ResetColor();
     /// @}