Type checker defines RESULT symbol for post condition of void operations

[nickbattle]

The RESULT symbol is defined for functions and operations that return a value. But not all operations return a value - some are void. However, the type checker defines a "void" valued RESULT symbol in this case. There should be no such symbol. For example:

operations
	op: () ==> ()
	op() == skip
	post RESULT > 0;    -- Error: Left hand of > is not ordered. Actual: ()

This ought to say that there is no symbol RESULT in scope.

[nickbattle]

Now fixed in ncb/development:

Error 3182: Name 'DEFAULT`RESULT' is not in scope in 'DEFAULT' (test.vdm) at line 4:10