Issue with double store charge slips
Allow voids after non-cash tender. Helpful with foodstamp or debit
situations where customer does not have sufficient balance to
pay for all items.
Attempt 239085235 to compensate for sticky/long key presses
Code cleanup on lane gui-modules:

Removed paycard-related pages. They now are maintained in the Paycards
plugin. Removed pos2.ajax.php since the default pos2.php uses AJAX
now. Removed old frame-based pages that were still lurking here for
no good reason.

Added a "basename(__FILE__) == basename(PHP_SELF)" to facilitate
unit testing pages. Took out hardcoded php "display_errors" directives.
Unit tests to verify gui-modules at least render without error