http-push.c: make CURLOPT_IOCTLDATA a usable pointer

Fixes a small bug affecting push to remotes which use some sort of
multi-pass authentication. In particular the bug affected SabreDAV as
configured by Box.com [1].

It must be a weird server configuration for the bug to have survived
this long. Someone should write a test for it.

[1] http://marc.info/?l=git&m=140460482604482

Signed-off-by: Abbaad Haider <abbaad@gmail.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-push.c

@@ -200,7 +200,7 @@ static void curl_setup_http(CURL *curl, const char *url,
 	curl_easy_setopt(curl, CURLOPT_READFUNCTION, fread_buffer);
 #ifndef NO_CURL_IOCTL
 	curl_easy_setopt(curl, CURLOPT_IOCTLFUNCTION, ioctl_buffer);
-	curl_easy_setopt(curl, CURLOPT_IOCTLDATA, &buffer);
+	curl_easy_setopt(curl, CURLOPT_IOCTLDATA, buffer);
 #endif
 	curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_fn);
 	curl_easy_setopt(curl, CURLOPT_NOBODY, 0);