fieser fehler, relativ alt. planes mehrfach defined (weil im header nicht extern)

src/common/kernel/plane.c

@@ -35,6 +35,8 @@
 #include <string.h>
 #include <stdlib.h>
 
+struct plane *planes;
+
 plane *
 getplane(const region *r)
 {

src/common/kernel/plane.h

@@ -57,7 +57,7 @@ typedef struct plane {
 	struct attrib *attribs;
 } plane;
 
-struct plane *planes;
+extern struct plane *planes;
 
 struct plane *getplane(const struct region *r);
 struct plane *findplane(int x, int y);