wmaker: fix incorrect type for variable in the global preference structure

As pointed by the new check script, the preference "show_clip_title" is
defined as a Boolean value in the preference loading function, which uses
the callback function "getBool", which expect a variable of type "char",
but the variable was not defined with that type.

This patch changes the type for the appropriate one to avoid possible
problems.

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

src/WindowMaker.h

@@ -459,7 +459,7 @@ extern struct WPreferences {
 
 	union WTexture *wsmbackTexture;
 
-	int show_clip_title;
+	char show_clip_title;
 
 	struct {
 		unsigned int nodock:1;                /* don't display the dock */