pgsql: Slow down driver even further.

Statements eligible to be automatically preparsed and kept in the
statement cache have to be parsed synchronously too to prevent
accidental reordering of parsing order.
pgsql: Reset prepared statement numbering upon cache invalidation.
Process.spawn_pike: Added launcher argument.
SSL.Connection: Fixed race condition with alert callbacks.

to_write() could get called with the pending alert before
the alert callback had determined what to do about the alert.

This caused the http to https redirect fallback in Roxen to fail,
due to to_write() having closed the stream before the callback
could steal it.
pgsql: Reset session urgently and deadlockfree.
pgsql: Improve debugging output and release all locks upon error.
pgsql: Close race between a parse in progress and a Sync.
pgsql: Notify callers early when connections are not possible.
rename aligned_alloc to xalloc_aligned

C11 defines aligned_alloc. This can lead to all kinds of confusion, so
lets rename our internal function.
Strings: silence a warning

Using a function instead of a macro takes care of casting the first
argument to a signed type, which silences a warning when the macro
was used with unsigned types.
pgsql: Delay accepting a commit until all portals have completed.
pgsql: Finetuned behaviour upon initial connection failure.
pgsql: Improve backtrace clarity of PGassist.