add print-change diff modes that do not use colour

Summary:
The colour characters currently added to the output of -print-changed=diff
and -print-changed=diff-quiet cause difficulties when capturing the output
and examining it in an editor. Change the function to not have the colour
characters and add 2 new choices (-print-changed=cdiff and
-print-changed=cdiff-quiet) to retain the existing functionality of adding
the colour characters.

Author: Jamie Schmeiser <schmeise@ca.ibm.com>
Reviewed By: aeubanks (Arthur Eubanks) yrouban (Yevgeny Rouban)
Differential Revision: https://reviews.llvm.org/D97398