wmaker: Added 'const' attribute to local variables

A number of these variable are not meant to be modified, so we
show this to the compiler.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

src/misc.c

@@ -167,7 +167,7 @@ void SlideWindows(Window *wins[], int n, int from_x, int from_y, int to_x, int t
 	int i;
 
 	/* animation parameters */
-	static struct {
+	static const struct {
 		int delay;
 		int steps;
 		int slowdown;