regex.c needs ULONG_WIDTH, not in standard limits.h

[Arnold Robbins]

Hi.

I just pulled a new copy of regex.c and tried to drop it into gawk. It
fails with ULONG_WIDTH undeclared.

It seems to be in Gnulib's limits.h replacement, but I'm not using that,
I rely on the standard limits.h.

Can this be fixed, or the change that uses it be reverted, please?

Thanks,

Arnold