Remove unnecessary cruft from the module example.

Remove unnecessary cruft from the module example.

This makes it more like a real module would be written while retaining it's utility as a teaching boilerplate.

* require Exporter instead of use with no import
* Declare and initialize variables together.
* Eliminate archaic RCS/CVS versioning clutter.
* Explain what @ISA does.
* Remove archaic (and slower) &func syntax from exporting
* Remove %EXPORT_TAGS.  It's not explained and rarely used.
* Remove redundant @EXPORT_OK
* Use cleaner $priv_func->() syntax rather than &$priv_func.
* Eliminate prototypes, they're clutter, rarely used and dangerous.

TonyC: update known_pod_issues.dat