Add header for foced fork variable. Don't know what it is good for yet. But why not...

plugins/python-renderer/src/force-fork.c

@@ -22,13 +22,13 @@
  * @author Mario Hüttel <mario.huettel@gmx.net>
  */
 
+#include <python-renderer/force-fork.h>
+
 /**
  * @addtogroup python-plugin
  * @{
  */
 
-#include <gds-render/output-renderers/external-renderer-interfaces.h>
-
 /* The precense of this variable tells the gds-render application to execute this plugin in a separate process
  * The variable's value is don't care
  */