Cleanup SWIG_VERSION definition

Add Swig_obligatory_macros which must be called by each
target language to define SWIG_VERSION correctly
in the generated code, as well as the language specific
macro SWIGXXX where XXX is the target language name.

Drop the #ifdef SWIGXXX that was previously generated -
I can't see the point of this and if users are defining
this macro somehow, then users will need to change this

Closes #1050

Source/Modules/java.cxx

@@ -456,7 +456,7 @@ public:
 
     Swig_banner(f_begin);
 
-    Printf(f_runtime, "\n\n#ifndef SWIGJAVA\n#define SWIGJAVA\n#endif\n\n");
+    Swig_obligatory_macros(f_runtime, "JAVA");
 
     if (directorsEnabled()) {
       Printf(f_runtime, "#define SWIG_DIRECTORS\n");