parents would be get remade, even if children were not really updated
by the commands executed for them. It also makes all the children have
the real modification time set if possible, so it should fix some other
timing weirdnesses...
- collapse childMade and make fields into flags and convert them to bits
CHILDMADE and REMAKE
- introduce FORCE flag that gets set in all the parents of a child that
has no sources and does not exist.
- set oodate if the FORCE flag is set, and not if CHILDMADE
- centralize the RECHECK into Make_Recheck() and use this in make.c and compat.c
- use Make_TimeStamp for all child -> parent timestamp propagations
4f3cc30bcc