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

tools/llvm-mc/llvm-mc.cpp

@@ -80,7 +80,7 @@ static int AsLexInput(const char *ProgName) {
   while (Tok != asmtok::Eof) {
     switch (Tok) {
     default:
-      Lexer.PrintMessage(Lexer.getLoc(), "driver: unknown token");
+      Lexer.PrintMessage(Lexer.getLoc(), "unknown token", "warning");
       Error = true;
       break;
     case asmtok::Error: