Update to latest BWIPP; add ZINT_QT6 option to cmake

docs: RM4SCC 4-State -> 4-State Customer code; man page, ChangeLog

frontend/tests/test_args.c

@@ -474,6 +474,7 @@ static void test_input(int index, int debug) {
 #else
 #define TEST_INPUT_AMPERSAND_EXPECTED "+++1.gif\000+++2.gif"
 #endif
+
     struct item {
         int b;
         int batch;