Normalize SourceMgr messages.

Normalize SourceMgr messages.
 - Don't print "Parsing" in front of every message.

 - Take additional "type" argument which is prepended to the message (with ": ")
   if given.

 - Update clients to print errors (warnings) as:
<filename>:<line number>: error(warning): ...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74489 91177308-0d34-0410-b5e6-96231b3b80d8