Glew has the problem that it has to be selected at build time if GLX or
EGL is supported by the library, and this in not encoded in the library
name, nor ABI, nor anything.
Then it's easy to get into the situation that a binary is built but
cannot run because glew supports an API different from the one used by
wxWidgets, or the binary fails to link in the end after all objects are
compiled.
epoxy can support both with the same library avoiding this problem.
epoxy is not initialized explicitly, replaced initialization with
version check where one was not done already.
It seems to be available as vcpkg https://vcpkg.link/ports/libepoxy
There are problems related to GL context switching on Windows which does
not seem to be used in kicad
https://github.com/anholt/libepoxy#known-issues-when-running-on-windows
There is also a problem related to multithreaded rendering on Windows
https://github.com/anholt/libepoxy/pull/265 It's harder to tell if
threading is used for rendering but it does not look like kicad is doing
anything complex enough to warrant using multiple rendering threads.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/20630
Fixes https://gitlab.com/kicad/code/kicad/-/issues/12543
Sometimes wxWidgets increments the subrelease to a non-zero value, and
since wxPython will report a subrelease, we must ensure we can get the
subrelease from the wx library properly, otherwise configure will fail
thinking the library isn't the same version as that used by wxPython.
Fixes: https://gitlab.com/kicad/code/kicad/-/issues/13887
