issue-#39 checking illegal use of SYSTEM.ADR function

[Josef Templ]

This issue is about a compiler bug. See http://redmine.blackboxframework.org/issues/39.
The compiler generates a TRAP 0 when SYSTEM.ADR is applied to a code procedure, which
does of course not give any sense.
A proposal for fixing this bug is available in CPC 1.7 rc5 by luowy.

The fix is straightforward and well done.
I have included the changes in topic branch issue-#39.
See the diffs in http://redmine.blackboxframework.org/pr ... 9f121aee0b.

Since there is not much to discuss about this issue, I create the voting
immediately.

- Josef