regcomp.c: Reverse order of setting, for speed

regcomp.c: Reverse order of setting, for speed

It's faster to append to an inversion list than to insert into the
middle.  The previous order of doing things guaranteed that the 2nd
thing done would be an insertion, hence slower than an append.  Now we
add the lowest ordinal character first, so there is a chance that both
will be appends