Decide whether to build http-push in the Makefile

The decision about whether to build http-push or not belongs in the
Makefile.  This follows Junio's suggestion to determine whether curl
is new enough to support http-push.

Signed-off-by: Nick Hengeveld <nickh@reactrix.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

http-push.c

@@ -6,8 +6,6 @@
 #include "blob.h"
 #include "http.h"
 
-#ifdef USE_CURL_MULTI
-
 #include <expat.h>
 
 static const char http_push_usage[] =
@@ -1426,10 +1424,3 @@ int main(int argc, char **argv)
 
 	return rc;
 }
-#else /* ifdef USE_CURL_MULTI */
-int main(int argc, char **argv)
-{
-	fprintf(stderr, "http-push requires curl 7.9.8 or higher.\n");
-	return 1;
-}
-#endif