wmaker: Cleaned dangerous function prototype usage

- remove extern declaration in source file, use header instead

- add inclusion of header defining the functions of the file to
get the compiler to cross-check them

- marked static the functions that should not be visible ouside
their file

src/geomview.c

@@ -1,6 +1,9 @@
 
 #include <WINGs/WINGsP.h>
 
+#include "geomview.h"
+
+
 typedef struct W_GeometryView {
 	W_Class widgetClass;
 	WMView *view;