* sinfo.ads, par-load.adb, sem_ch10.adb, lib-load.ads, lib-load.adb
sem_ch12.adb: Change the meaning of the Library_Unit attribute to
include units containing instantiations, as well as units that are
generic instantiations.
* sem.adb: Include dependents and corresponding specs/bodies in the
unit walk.
* gcc-interface/Make-lang.in:
sem now depends on s-bitops, because of the packed array of Booleans.