ncurses 6.2 - patch 20200718

+ reduce redefinition-warnings for KEY_EVENT when building with Visual
  Studio C++.
+ define NCURSES_STATIC when compiling programs to link with static
  libraries, to work with MinGW vs Visual Studio C++.
> additional changes for building with Visual Studio C++ and msys2
  (reports/patches by "Maarten Anonymous")
+ modify c++/Makefile.in to set the current directory while compiling
  the main program, so the linker can find related objects.
+ several changes to allow the c++/demo program to compile/link.
+ change an ifdef in test-directory, to use VC++ wide-character funcs.