regcomp.c: Add ability to have compiled-in inversion lists

regcomp.c: Add ability to have compiled-in inversion lists

This adds a routine that will take a C array and quickly create an
inversion list that points to that array.  Thus the array had better be
exactly the internal form that is required for an inversion list.  To
make sure that this doesn't get out of sync, a new field in the list's
header is created that is a combination of
version-number/inversion-list-type.