Workaround v4l2 drivers that do not behave correctly while enumerating inputs, standard, tuner, or format.

Crop/AR settings can now be changed by the video filters.
Crop/AR changes done by the decoder are now applied to the exact
picture and without any picture loss (before this patch, it was applied
too soon and due to the recreation of the vout display, some pictures where
lost).

They were previously lost.

Moved up two functions.

Now vout_SetDisplayCrop() takes crop parameters relative to the visible part.

The old code used the current thread affinity.

It is more of a workaround, a cleaner way to configure video filters
will need to be done.

The variables are void, not boolean.

We want compilation to fail if this is missing.

This reverts commit 884eaa35.

This will not override a previous hint_distro.

contribs: Use the gcc toolchain installed in /usr/bin instead of /Developer because the latter is no reliable path as it can be installed anywhere