Revert "Don't require -re suffix on -verify directives with regexes."

This patch was submitted to the list for review and didn't receive a LGTM.

(In fact one explicit objection and one query were raised.)

This reverts commit r197295.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197299 91177308-0d34-0410-b5e6-96231b3b80d8