Should fix #1536

Reported by Drew Yao

Tooltips still need to be added

The whole point of keeping the m4 and po/Makefile.in.in is to not need
to have the same version all over the place anyway, otherwise we might
as well put all these files to .gitignore...

Remove some old m4 macros as well.

Now that we actually have _ALL_ the gettext m4 macros in m4/, autopoint
is useless. That was not the case last time this hack was attempted.

It was a bit clumsy to have to modify it through bootstrap.

I assume PATH is already exported for obvious reasons.

Default to no backup when updating po files

Includes an array of not-to-be-used keys

Shows modifier keys with their corresponding symbols instead of 'Alt', etc.

Saving combinations of multiple keys won't crash anymore, but work as expected

and fix the M4 ignore rules

This reverts commit 8b71b104.
Most developers did not update their gettext install
Bumping gettext requirement is useless.

interaction: No need to call vlc_object_join() now.

interaction: Keep a libvlc's global interaction object reference around, and properly release it when done.

objects: Send a vlc_object_kill from vlc_object_destroy() to make sure vlc_object_release() can properly free all the allocated resources when the refcount reach zero.

Previously you need to send a vlc_object_kill() prior to a vlc_object_release() to get your object actually destroyed, which rendered the refcounting unusuable in some cases.