lib: the number four in a sequence is the "fourth"

Spelling is hard

Closes #9535

lib/asyn-ares.c

@@ -746,7 +746,7 @@ static void addrinfo_cb(void *arg, int status, int timeouts,
  * Curl_resolver_getaddrinfo() - when using ares
  *
  * Returns name information about the given hostname and port number. If
- * successful, the 'hostent' is returned and the forth argument will point to
+ * successful, the 'hostent' is returned and the fourth argument will point to
  * memory we need to free after use. That memory *MUST* be freed with
  * Curl_freeaddrinfo(), nothing else.
  */

lib/asyn.h

@@ -148,7 +148,7 @@ CURLcode Curl_resolver_wait_resolv(struct Curl_easy *data,
  * Curl_resolver_getaddrinfo() - when using this resolver
  *
  * Returns name information about the given hostname and port number. If
- * successful, the 'hostent' is returned and the forth argument will point to
+ * successful, the 'hostent' is returned and the fourth argument will point to
  * memory we need to free after use. That memory *MUST* be freed with
  * Curl_freeaddrinfo(), nothing else.
  *

lib/hostip6.c

@@ -96,8 +96,8 @@ static void dump_addrinfo(struct connectdata *conn,
  * non-ares version).
  *
  * Returns name information about the given hostname and port number. If
- * successful, the 'addrinfo' is returned and the forth argument will point to
- * memory we need to free after use. That memory *MUST* be freed with
+ * successful, the 'addrinfo' is returned and the fourth argument will point
+ * to memory we need to free after use. That memory *MUST* be freed with
  * Curl_freeaddrinfo(), nothing else.
  */
 struct Curl_addrinfo *Curl_getaddrinfo(struct Curl_easy *data,

lib/http.c

@@ -3618,7 +3618,7 @@ CURLcode Curl_http_header(struct Curl_easy *data, struct connectdata *conn,
        The second format was added since Sun's webserver
        JavaWebServer/1.1.1 obviously sends the header this way!
        The third added since some servers use that!
-       The forth means the requested range was unsatisfied.
+       The fourth means the requested range was unsatisfied.
     */
 
     char *ptr = headp + strlen("Content-Range:");