Generate valid code for "dereferencing" pointers to void.

This covers code like the following, which is very dubious but does not seem to be clearly prohibited by the standards:

int main(void) {
        void *vp;
        *vp;
}

Previously, this would do an indirect load of a four-byte value at the location, but then treat it as void. This could lead to the four-byte value being left on the stack, eventually causing a crash. Now we just evaluate the pointer expression (in case it has side effects), but effectively cast it to void without dereferencing it.

Expression.pas

@@ -4564,7 +4564,7 @@ case tree^.token.kind of
          isVolatile := tqVolatile in lType^.qualifiers;
          if lType^.kind = scalarType then
             if lType^.baseType = cgVoid then
-               Gen2t(pc_ind, ord(isVolatile), 0, cgULong)
+               Gen2(pc_cnv, cgULong, cgVoid)
             else
                Gen2t(pc_ind, ord(isVolatile), 0, lType^.baseType)
          else if lType^.kind = pointerType then