define setUp and tearDown under UNITY_WEAK_PRAGMA

The intent of UNITY_WEAK_PRAGMA is that we have weak symbols for setUp
and tearDown in unity.o, so that developers can override these symbols
if needed but the link works right if they are not defined.

In order to do this using #pragma, the pragma and the definition of the
function (not the declaration) need to be present in the same translation
unit (source code file).

Previously, the UNITY_WEAK_PRAGMA code was just declaring the setUp
function, but not defining it, which means that developers had to add an
empty setUp function to their tests in order to link.

src/unity.c

@@ -1231,9 +1231,9 @@ void UnityIgnore(const char* msg, const UNITY_LINE_TYPE line)
     UNITY_WEAK_ATTRIBUTE void tearDown(void) { }
 #elif defined(UNITY_WEAK_PRAGMA)
 #   pragma weak setUp
-    void setUp(void);
+    void setUp(void) { }
 #   pragma weak tearDown
-    void tearDown(void);
+    void tearDown(void) { }
 #else
     void setUp(void);
     void tearDown(void);