Merge pull request alex85k#3 from nazar-pc/patch-1

Meson build system support by @nazar-pc

Build static lib if not defined WINGETOPT_SHARED_LIB

export global variables to dll if needed

support building shared library (for vcpkg)

support building shared library (for vcpkg)

more gitignore lines

Merge pull request alex85k#2 from KOLANICH/master

Fixed a compile error for c++ because of missing const