DMATAMATRIX: fix look ahead BASE256 use of dm_text_sp_cnt() on switching;
simplify dm_add_tail()
GUI: check suffixes on save so don't go into error state;
use native path for Save As clipboard message
CODE128: use gs1_check_digit() for NVE18 and EAN14
add specify rows option (option_3) (#204);
warn if cols increased from specified (back-incompatible);
move table definitions from "pdf417.h" to new "pdf417_tabs.h" and
make INTERNAL_DATA and share with composite.c (saves ~10K);
prefix routines and tables with "pdf_";
some small performance improvements through if/elses, pdf_textprocess()
& pdf_numbprocess() loop simplifications
MICROQR: fix debug access crash on printing non-NUL-terminating binary
DATAMATRIX: fix missing ++ from "[tp]" at C40/TEXT EOD processing of GS1
(though probably never reached); use "[tp++]" throughout
Add const to static tables missing it and also to some variables
Change "debug" -> "debug_print" throughout
GRIDMATRIX, MAXICODE, MICROPDF417, PDF417, QRCODE, ULTRA
DOTCODE: use pre-calculated generator poly coeffs in Reed-Solomon for
performance improvement
PDF417/MICROPDF417: use common routine pdf417_initial()
GUI: code lines <= 118, shorthand widget_obj(),
shorten calling upcean_addon_gap(), upcean_guard_descent()
various backend: var name debug -> debug_print
