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
PLESSEY: add options NCR weighted mod-10, hide check digit(s) in HRT
test suite: now runnable under MSVC 2019, 2017, 2015, MinGW/MSYS
win32/README: update with MSVC 2019 and CMake instructions
