Intercept CTRL+C

Intercept the ctrl+x keystrock and close properly the lektord daemon.

inc/lektor/common.h

@@ -137,8 +137,7 @@ typedef volatile enum {
 #define not_implemented() __not_implemented(__func__,__FILE__,__LINE__)
 extern void __not_implemented(const char *func, char *file, int line);
 
-#define UNUSED(...) __unused((void *) __VA_ARGS__)
-void __unused(void *, ...);
+#define UNUSED __attribute__((unused))
 
 long get_mtime(const char *path);