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/moveres.c

@@ -37,6 +37,7 @@
 #include "funcs.h"
 #include "actions.h"
 #include "workspace.h"
+#include "placement.h"
 
 #include "geomview.h"
 #include "screen.h"