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/osdep_linux.c

@@ -12,6 +12,8 @@
 #include <WINGs/WUtil.h>
 
 #include "wconfig.h"
+#include "funcs.h"
+
 
 #define	RETRY( x )	do {				\
 				x;			\