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
This will pick up the local copies of the test data by default, without
needing to create a subdirectory in the backend/tests path and executing
the tests from there. The Current Working Directory can be set if this
proves to be insufficient
