lib: strndup/memdup instead of malloc, memcpy and null-terminate

- bufref: use strndup
 - cookie: use strndup
 - formdata: use strndup
 - ftp: use strndup
 - gtls: use aprintf instead of malloc + strcpy * 2
 - http: use strndup
 - mbedtls: use strndup
 - md4: use memdup
 - ntlm: use memdup
 - ntlm_sspi: use strndup
 - pingpong: use memdup
 - rtsp: use strndup instead of malloc, memcpy and null-terminate
 - sectransp: use strndup
 - socks_gssapi.c: use memdup
 - vtls: use dynbuf instead of malloc, snprintf and memcpy
 - vtls: use strdup instead of malloc + memcpy
 - wolfssh: use strndup

Closes #12453

lib/formdata.c

@@ -779,11 +779,9 @@ static CURLcode setname(curl_mimepart *part, const char *name, size_t len)
 
   if(!name || !len)
     return curl_mime_name(part, name);
-  zname = malloc(len + 1);
+  zname = Curl_strndup(name, len);
   if(!zname)
     return CURLE_OUT_OF_MEMORY;
-  memcpy(zname, name, len);
-  zname[len] = '\0';
   res = curl_mime_name(part, zname);
   free(zname);
   return res;