Restore SnapToEdge and MoveToEdge default keybinds

When adding the fallback keybinds we add them as string but expect them being an int.
This commit fixes that by using the same parsing routines that are used when parsing
user supplied configuration.

Fixes 1ee8715d57
actions: use enum for _ToEdge action

src/action.c

@@ -159,7 +159,7 @@ action_arg_add_int(struct action *action, const char *key, int value)
 }
 
 void
-action_arg_from_xml_node(struct action *action, char *nodename, char *content)
+action_arg_from_xml_node(struct action *action, const char *nodename, const char *content)
 {
 	assert(action);