Either shared or static (or both) libraries can be built now.
Executables (zint and zint-qt) are linked with the static library if the shared
library it not built.
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