Add a -dump-trc frontend option to print the type refinement context hierarchy

This is useful for debugging and testing.

Swift SVN r30383

lib/Driver/Driver.cpp

@@ -938,6 +938,7 @@ void Driver::buildOutputInfo(const ToolChain &TC, const DerivedArgList &Args,
     case options::OPT_dump_parse:
     case options::OPT_dump_ast:
     case options::OPT_print_ast:
+    case options::OPT_dump_trc:
       OI.CompilerOutputType = types::TY_Nothing;
       break;