syntax-check: Reorganize file

syntax-check: Reorganize file

Due to the way make works, we are not forced to follow a strict
order in defining rules and variables. In fact _sc_search_regexp,
which is used by all checks, is only defined halfway through the
file.

Shuffle things around so that the things that we need to look at
the most frequently are closer to the top of the file.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>