Remove defaulted 'tid' parameter to ptid_t constructor

I wanted to find, and potentially modify, all the spots where the
'tid' parameter to the ptid_t constructor was used.  So, I temporarily
removed this parameter and then rebuilt.

In order to make it simpler to search through the "real" (nonzero)
uses of this parameter, something I knew I'd have to do multiple
times, I removed any ", 0" from constructor calls.

Co-Authored-By: John Baldwin <jhb@FreeBSD.org>