they render correctly when have RGBA alpha channel
- GUI: update_preview() after Data Dialog return to ensure preview in sync
- GUI: add automatic info feedback to "Automatic" combo item of size/row/height
comboboxes
- backend_qt: always call getMaxRectsRightBottom() for render fudge; use
ZBarcode_Clear() instead of ZBarcode_Delete() after 1st call
- update BWIPP to latest & add some MICROQR tests to exercise optimize change