Fix unexpected warning on typedef enum without { } 

(related to issue #2)

/** This should not trigger an undefined warning */
#define XYZ typedef enum bla;

/** This should */
typedef enum { One, Two } xyz;

/** This should not */
 #ifndef NS_ENUM
 #define NS_ENUM(_type, _name) enum _name : _type _name; enum _name : _type
 #endif