config-parser: fix `short_name` type

This field is populated with chars, compared to chars and printed as
a char. It should probably be a char.

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Daniel Stone <daniels@collabora.com>

shared/config-parser.h

@@ -64,7 +64,7 @@ enum weston_option_type {
 struct weston_option {
 	enum weston_option_type type;
 	const char *name;
-	int short_name;
+	char short_name;
 	void *data;
 };