regexp.h: Move bits around

regexp.h: Move bits around

make regen needed.

This commit moves some bits in extflags around so that all the unallocated
ones are at the boundary between the unshared portion and the portion
shared with op.h.  This allows them to be allocated in the future to go
either way, without affecting binary compatibility at that time.

The high-order bits are unaffected, but the low order ones move to fill
the gap.