MFC r298521;

MFC r298521;
regex: prevent two improbable signed integer overflows.

In matcher() we used an integer to index nsub of type size_t.
In print() we used an integer to index nstates of type sopno,
typedef'd long.
In both cases the indexes never take negative values.

Match the types to avoid any error.

git-svn-id: svn://svn.freebsd.org/base/stable/10@298726 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f