#40 m_medic.pas has strange non-standard convertions

[Leonel Togniolli]

In m_medic.pas, there is code that has been converted
to:

self^.monsterinfo.aiflags :=self^.monsterinfo.aiflags and
((AI_HOLD_FRAME+1)*(-1))

when everywhere else it is:

self^.monsterinfo.aiflags :=self^.monsterinfo.aiflags and
not AI_HOLD_FRAME;

which is more readable and is guaranteed to work
correctly. All relevant code should be changed.