New implementation of complex search criteria using \(, \), -a because

New implementation of complex search criteria using \(, \), -a because
the old implementation got lost in the Berkeley to SQLite switch.
Note that this is not just feature creep, but required for upcoming
database format cleanup and simplification.

The following takes less than half a second on my Z61m ThinkPad:
time ./obj/apropos An=kettenis -a \( Cd=vnet -o Xr=vbus \)