Avoid newer check macros

Some of these `ck_assert_*` macros were only added in check 0.9.9.
Quite a few system package managers (e.g., Debian/Ubuntu) still ship
0.9.8.  I'd rather use the old macros for now, rather than forcing more
systems to install a non-standard package upgrade.  (Super-old systems
like RHEL5 still need a compiled version of a more “recent” check.)