New hook post_config_hooks.

New hook post_config_hooks.

This is run after all configuration has been processed.  That is,
after command-line options processing.

It is also run before other exits where you can reasonably expect
configuration to be complete (--dump, -e <expr>).

It is not run before -E.  If you want to run in combination with -E
then add "run_hooks post_config_hooks" to the expression (or to a
previous -E option).  However, bear in mind that this may preempt any
magic the hooks might otherwise do after subsequent configuration
option processing.

Signed-off-by: Martin Schwenke <martin@meltin.net>