Fix va_start compiler warning

../src/libinput.c:56:17: warning: passing an object that undergoes default
argument promotion to 'va_start' has undefined behavior [-Wvarargs]

The enum's size is compiler-defined, so the enum gets promoted to whatever the
compiler chose. That promotion is undefined, so let's use an int here.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Armin Krezović <krezovic.armin@gmail.com>
Tested-by: Armin Krezović <krezovic.armin@gmail.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>

src/libinput.c

@@ -46,7 +46,7 @@
 static inline bool
 check_event_type(struct libinput *libinput,
 		 const char *function_name,
-		 enum libinput_event_type type_in,
+		 unsigned int type_in,
 		 ...)
 {
 	bool rc = false;