ncurses 6.2 - patch 20200704

+ modify version-check with Ada generics to use the same pattern as in
  the check for supported gnat versions (report by Pascal Pignard).
> additional changes for building with Visual Studio C++ and msys2
  (patches by "Maarten Anonymous"):
+ adjust headers/declarations to provide for "dllimport" vs "dllexport"
  declarations when constructing DLLs, to worko with Visual Studio C++.