fix for -fno-common
https://github.com/MegaGlest/megaglest-source/commit/5a3520540276a6fd06f7c88e571b6462978e3eab

Index: source/shared_lib/sources/feathery_ftp/ftpRuntime.c
--- source/shared_lib/sources/feathery_ftp/ftpRuntime.c.orig
+++ source/shared_lib/sources/feathery_ftp/ftpRuntime.c
@@ -30,6 +30,13 @@
 #include "ftp.h"
 #include "ftpMessages.h"
 
+int VERBOSE_MODE_ENABLED;
+
+ftpFindExternalFTPServerIpType ftpFindExternalFTPServerIp;
+ftpAddUPNPPortForwardType              ftpAddUPNPPortForward;
+ftpRemoveUPNPPortForwardType   ftpRemoveUPNPPortForward;
+ftpIsValidClientType            ftpIsValidClient;
+ftpIsClientAllowedToGetFileType ftpIsClientAllowedToGetFile;
 
 /**
  * @brief server-sockets that listens for incoming connections
