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/test/nxt_http_parse_test.c

@@ -753,7 +753,7 @@ nxt_http_parse_test_request_line(nxt_http_request_parse_t *rp,
         return NXT_ERROR;
     }
 
-    if (nxt_memcmp(rp->version.str, test->version, 8) != 0) {
+    if (memcmp(rp->version.str, test->version, 8) != 0) {
         nxt_log_alert(log, "http parse test case failed:\n"
                            " - request:\n\"%V\"\n"
                            " - version: \"%*s\" (expected: \"%*s\")", request,

src/test/nxt_tests.c

@@ -41,7 +41,7 @@ main(int argc, char **argv)
 #if (NXT_TEST_RTDTSC)
 
     if (nxt_process_argv[1] != NULL
-        && nxt_memcmp(nxt_process_argv[1], "rbm", 3) == 0)
+        && memcmp(nxt_process_argv[1], "rbm", 3) == 0)
     {
         if (nxt_rbtree1_mb_start(thr) != NXT_OK) {
             return 1;

src/test/nxt_utf8_file_name_test.c

@@ -129,7 +129,7 @@ nxt_utf8_file_name_test(nxt_thread_t *thr)
 
             nxt_file_close(&task, &lc_file);
 
-            if (n != 4 || nxt_memcmp(utf8, test, 4) != 0) {
+            if (n != 4 || memcmp(utf8, test, 4) != 0) {
                 nxt_log_alert(thr->log, "nxt_file_read() mismatch");
 
                 nxt_file_delete(lc_file.name);

src/test/nxt_utf8_test.c

@@ -59,7 +59,7 @@ nxt_utf8_overlong(nxt_thread_t *thr, u_char *overlong, size_t len)
 
         size = (p != NULL) ? p - utf8 : 0;
 
-        if (len != size || nxt_memcmp(overlong, utf8, size) != 0) {
+        if (len != size || memcmp(overlong, utf8, size) != 0) {
 
             u = 0;
             for (i = 0; i < len; i++) {