Compiler: Fixed updating of PROGRAM_{NEEDS,USES}_PARENT.

low_inherit() may get called with a parent offset of 24
(OBJECT_PARENT + 42) or 25 (INHERIT_PARENT + 42) when
called from decode_value().

Make sure we don't start zapping flags in random programs
on the compiler stack when this happens.

Fixes [LysLysKOM 20258894] and [LysLysKOM 20273476]/[Pike 13584].