xmp

In Exiv2/exiv2#2219 (comment) we discussed about the possibility of having some dead code in our codebase around the EXV_HAVE_MMAP definition:

As far as I can see we have the following preprocessor conditions:
```cpp
#if defined EXV_HAVE_MMAP && defined EXV_HAVE_MUNMAP
...
#elif defined WIN32 && !defined __CYGWIN__
...
#else
...  <-- This is t

Hi,

I have a huge collection of photos, and think it would be nice to get back to the last position in image list when reopening the app, some kind of session restore in a way.
Thanks a lot for your work

Raphael

We used to have this (tracked in felixc/rexiv2#18, set up in felixc/rexiv2@90ae678), but it had to be removed in felixc/rexiv2@1aff63e because the travis-cargo project we'd been using had broken ages ago was no longer actually uploading coverage info.