Return int from mexp_expect

Return int from mexp_expect

GCC 13 highlights the mismatch between int and enum in the declared vs
implemented return type.  The return types are in this case
compatible, but it's not generally safe to implicitly convert between
int and enum.

miniexpect.c:248:1: warning: conflicting types for ‘mexp_expect’ due to enum/integer mismatch; have ‘enum mexp_status(mexp_h *, const mexp_regexp *, pcre2_match_data_8 *)’ {aka ‘enum mexp_status(mexp_h *, const mexp_regexp *, struct pcre2_real_match_data_8 *)’} [-Wenum-int-mismatch]
  248 | mexp_expect (mexp_h *h, const mexp_regexp *regexps,
      | ^~~~~~~~~~~
In file included from miniexpect.c:41:
miniexpect.h:100:12: note: previous declaration of ‘mexp_expect’ with type ‘int(mexp_h *, const mexp_regexp *, pcre2_match_data_8 *)’ {aka ‘int(mexp_h *, const mexp_regexp *, struct pcre2_real_match_data_8 *)’}
  100 | extern int mexp_expect (mexp_h *h, const mexp_regexp *regexps,
      |            ^~~~~~~~~~~