determine_if_regex: add pseudo REG_FORCE flag
determine_if_regex: add pseudo REG_FORCE flag

for rewrites it is necessary to have regular expression with
sub-expression matching (even when there are no sub-expressions) because
the matched part needs to be replaced, and we need the position of it.

tjamesturner/carbon-c-relay,grobian/carbon-c-relay,zzl0/carbon-c-relay,lyft/carbon-c-relay,lyft/carbon-c-relay,rtoma/carbon-c-relay,Skyscanner/carbon-c-relay,tjamesturner/carbon-c-relay,piotr1212/carbon-c-relay,grobian/carbon-c-relay,piotr1212/carbon-c-relay,rtoma/carbon-c-relay,Skyscanner/carbon-c-relay,piotr1212/carbon-c-relay,lyft/carbon-c-relay,piotr1212/carbon-c-relay,grobian/carbon-c-relay,zzl0/carbon-c-relay