BC412: add to backend_tcl; add skeleton test

GUI: allow for Qt not parsing #if's in slots (copy_to_clipboard_png())

backend_qt/backend_vc8.pro

@@ -55,6 +55,7 @@ HEADERS +=  ../backend/aztec.h \
 SOURCES += ../backend/2of5.c \
            ../backend/auspost.c \
            ../backend/aztec.c \
+           ../backend/bc412.c \
            ../backend/bmp.c \
            ../backend/codablock.c \
            ../backend/code.c \