(travis) Stop auto-upgrading everything on non-clean installs

It adds little value currently and makes version-specific installs difficult
(see next commit)
(travis) Accommodate a slow mirror grrrrr
Adjust for SQLA's API change 966200cc8
Fix copy() assuming all columns are native
Make sure the me-relname-flip does not affect any error text
Yet another missed sanity check in the relcond resolver

rel/col duality is just hateful
Ensure undef_on_null_fk does not affect non-introspectable custom conds
A more robust column equality extractor

It is a mistake to reach into $ret->{condition} - it may very well be a
non-hash structure. Also replace the silly regexping with the (already
regexed out) results of the info resolver
Ensure the custom rel cond resolver does not trigger forgotten compat shim

During the rush to get custom rels out the door (this is why rushing
fucking sucks), a697fa31 introduced a shortsighted workaround into
::SQLMaker::_from_chunk_to_sql(). This code slipped consequent review
and made its way into the codebase... 4 FUCKING YEARS AGO!!! >:(

Since it is not known how much stuff relies on the insanity being there
(moreover we have tests that rely on it) leave things as is for the time
being. The only change is  making the cond resolver *completely* oblivious to
the "single-element hash" workaround (albeit via a silly hack).

In the process exposed that ora-joins module is entirely incapable
of understanding non-equality conds... fml

See next commits for added warnings, etc.
Split DBIC from SQLMaker test (deprecated in next commit)
Put in place deprecation forgotten for several years

More info and rationale in the commit msg of c200d949
Ensure the tempextlib is available at distbuild time

Missed one spot to load ::_Util during bbcc1fe8