- PDF417/MICROPDF417: use latch not ps shift for padding when

spanning Text segments to avoid affecting 1st char of 2nd segment
- PDF417/MICROPDF417: add optimized encoding, FAST_MODE for
  previous scheme; formatting changes
- common.c/h: add `cnt_digits()`, comments in include and make more
  consistent, minor code fiddling
- DOTCODE: replace `dc_n_digits()` with new `cnt_digits()`
- test_qr: fix `test_qr_perf()`
- composite: minor code fiddling
- library: debug dump HIBC-processed input
- BWIPP: update to latest

backend_qt/backend_qt.pro

@@ -56,6 +56,7 @@ HEADERS +=  ../backend/aztec.h \
             ../backend/pcx.h \
             ../backend/pdf417.h \
             ../backend/pdf417_tabs.h \
+            ../backend/pdf417_trace.h \
             ../backend/qr.h \
             ../backend/reedsol.h \
             ../backend/reedsol_logs.h \