curl: Fix warnings on 64-bit Mac OS X build

Re-apply change from commit v2.6.0~921 (Fix warnings on 64-bit Mac OS X
build, 2007-11-05) on updated upstream curl.

Utilities/cmcurl/lib/ftp.c

@@ -3790,8 +3790,9 @@ CURLcode ftp_perform(struct connectdata *conn,
 
   infof(conn->data, "ftp_perform ends with SECONDARY: %d\n", *connected);
 
-  if(*dophase_done)
+  if(*dophase_done) {
     DEBUGF(infof(conn->data, "DO phase is complete1\n"));
+  }
 
   return result;
 }