Add mouse binding pointer position configuration

Add the `--whole-window` switch for mouse bindings. This switch controls
what part of the container the pointer must be over to trigger a mouse
binding. The default is to only trigger mouse bindings over the
titlebars. With this switch, a mouse binding will be triggered over the
main part of the window as well.

This is a breaking change to the previous behavior, which would trigger
a mouse binding with a modifier over any part of the window.

fixes #1429

include/bindings.h

@@ -24,7 +24,7 @@ const char *DEFAULT_BINDING_MODE;
  *
  */
 Binding *configure_binding(const char *bindtype, const char *modifiers, const char *input_code,
-                           const char *release, const char *command, const char *mode);
+                           const char *release, const char *whole_window, const char *command, const char *mode);
 
 /**
  * Grab the bound keys (tell X to send us keypress events for those keycodes)