Get the 2's compliment of the unsigned int `number` when printing results...

Get the 2's compliment of the unsigned int `number` when printing results without relying on problematic recasting of a negated int. (see #439)

src/unity.c

@@ -327,7 +327,7 @@ void UnityPrintNumber(const UNITY_INT number_to_print)
     {
         /* A negative number, including MIN negative */
         UNITY_OUTPUT_CHAR('-');
-        number = (UNITY_UINT)-number_to_print;
+        number = (~number) + 1;
     }
     UnityPrintNumberUnsigned(number);
 }