strlist_index
index = strlist_index(p, len, name);
assert(strlist_index(sl, slsize, "non-existent") == -1);
assert(strlist_index(sl, slsize, "zero") == 0);
assert(strlist_index(sl, slsize, "one") == 1);
assert(strlist_index(sl, slsize, "two") == 2);
assert(strlist_index(sl, slsize, "three") == 3);
assert(strlist_index(sl, slsize, "four") == 4);
assert(strlist_index(sl, slsize, "five") == 5);
int strlist_index(const char *, size_t, const char *);