PR21065: dtrace .d usdt parser: tolerate probe ... (...) : (...); syntax

PR21065: dtrace .d usdt parser: tolerate probe ... (...) : (...); syntax

Allow our /usr/bin/dtrace-impersonating usdt-.d file parser to take in
those .d files that use the "arguments passed to probe consumers"
extended syntax:

provider {
    probe FOO (int foo, char *bar) : (int foo, string bar);
}

We just quietly ignore the latter part though, so the systemtap script
sees the application's raw DTRACE_PROBE* argument list.