In wxFileName::Exists, make wxFILE_EXISTS_SYMLINK imply wxFILE_EXISTS_NO_FOLLOW

[dghart]

As mentioned in #14542, it makes no sense to call wxFileName::Exists(wxFILE_EXISTS_SYMLINK) without preventing symlink dereferencing; otherwise it would always return false. The attached patch implements this.

The default flag wxFILE_EXISTS_ANY contains wxFILE_EXISTS_SYMLINK, so wxFILE_EXISTS_NO_FOLLOW will be auto-added for this too. I suppose it would therefore be sensible to add it explicitly, though I've not done so here.

[vadz]

Interesting that you decided to do it like this, is there any advantage compared to just setting wxFILE_EXISTS_NO_FOLLOW bit in wxFILE_EXISTS_SYMLINK itself?

I.e. make it so that testing wxFILE_EXISTS_SYMLINK & wxFILE_EXISTS_NO_FOLLOW would simply return non-zero. Is there some problem with doing this? Because it seems simpler to me than the current patch...

[dghart]

Replying to vadz:

Interesting that you decided to do it like this, is there any advantage compared to just setting wxFILE_EXISTS_NO_FOLLOW bit in wxFILE_EXISTS_SYMLINK itself?

No, it just didn't occur to me.

The alternative patch implements it that way. I had to set the wxFILE_EXISTS_NO_FOLLOW bit in wxFILE_EXISTS_ANY too, or Exists(wxFILE_EXISTS_ANY) would miss symlinks, and zero it out before testing for symlinks, so there's not much simplification.

Or maybe I missed something else...

[VZ]

(In [72777]) Make wxFILE_EXISTS_SYMLINK work on its own, without wxFILE_EXISTS_NO_FOLLOW.

Include the wxFILE_EXISTS_NO_FOLLOW bit in wxFILE_EXISTS_SYMLINK definition to
allow using just wxFileName::Exists(wxFILE_EXISTS_SYMLINK) which used to never
work because the link was followed.

Closes #14777.