Removed the unsafe nxt_memcmp() wrapper for memcmp(3).

The casts are unnecessary, since memcmp(3)'s arguments are 'void *'.
It might have been necessary in the times of K&R, where 'void *' didn't
exist.  Nowadays, it's unnecessary, and _very_ unsafe, since casts can
hide all classes of bugs by silencing most compiler warnings.

The changes from nxt_memcmp() to memcmp(3) were scripted:

$ find src/ -type f \
  | grep '\.[ch]$' \
  | xargs sed -i 's/nxt_memcmp/memcmp/'

Reviewed-by: Andrew Clayton <a.clayton@nginx.com>
Signed-off-by: Alejandro Colomar <alx@nginx.com>

src/nxt_php_sapi.c

@@ -1036,7 +1036,7 @@ nxt_php_dynamic_request(nxt_php_run_ctx_t *ctx, nxt_unit_request_t *r)
         script_name = *ctx->index;
 
     } else if (path.length < 4
-               || nxt_memcmp(path.start + (path.length - 4), ".php", 4) != 0)
+               || memcmp(path.start + (path.length - 4), ".php", 4) != 0)
     {
         char         tpath[PATH_MAX];
         nxt_int_t    ec;