Add compliant height, using ZINT_COMPLIANT_HEIGHT flag for back-compatibility

Rename barcode funcs to same as BARCODE_XXX name
library: barcode funcs array for dispatch, used for ZBarcode_ValidID() also
general: change is_sane() comparison to nonzero from ZINT_ERROR_INVALID_OPTION
MAILMARK: fuller error messages
CODABAR: add option to show check character in HRT
zint.h: use 0xNNNN for OR-able defines
GUI: add guard descent height reset button, add Zint version to window title,
  static get_zint_version() method, use QStringLiteral (QSL shorthand),
  use SIGNAL(toggled()), add errtxt "popup" and status bar, add icons,
  add saveAs shortcut, add main menu, context menus and actions, add help,
  reset_view() -> reset_colours(), add copy to clipboard as EMF/GIF/PNG/TIF,
  lessen triggering of update_preview(), shorten names of getters/setters,
  simplify/shorten some update_preview() logic in switch,
  CODEONE disable structapp for Version S
qzint.cpp: add on_errored signal, add missing getters, add test

frontend_qt/main.cpp

@@ -30,6 +30,8 @@ int main(int argc, char *argv[])
     QApplication app(argc, argv);
 
     MainWindow w;
+    // Seem to need to do this before showing the window
+    w.setWindowTitle(w.windowTitle() + ' ' + MainWindow::get_zint_version());
     w.show();
     return app.exec();
 }