src/types.c, regress/: Use checklabel hook to parse PTR query domains.

src/types.c, regress/: Use checklabel hook to parse PTR query domains.

A PTR with forward-lookup checking needs to parse the original question
into an address, so as to have something to compare the results of the
forward queries against.  Previously this was done in pa_ptr, when the
first PTR answer came in.  But parsing can fail, and is a simple
syntactic computation on the input domain name, so it seems rather
unfortunate to delay checking the name until an answer has come in.  Now
that we have the checklabel hook, then, we might as well use it here.
(Indeed, this is in fact the reason for introducing it.)

Unfortunately, this check now rejects a number of queries early, which
previously would have resulted in a query and maybe a NODATA or NXDOMAIN
answer, but in exactly the way we just rigged all of the test cases.  So
we remove the temporary hack to adns_submit and everything stays good.
Right?

Signed-off-by: Mark Wooding <mdw@distorted.org.uk>