framebuffer: Correctly fix framebuffer with width < line_length

Last commit had some bugs and this case still didn't work.

Signed-off-by: Guillaume Clement <gclement@baobob.org>
signals: Restore the console state on a segmentation fault

This allows to at least see the error in case this happens.

Signed-off-by: Guillaume Clement <gclement@baobob.org>
signals: Allow to pause and resume the framebuffer

Ultimately, this would allow to debug desco from a normal
debugger. Currently this is not ideal because we don't save the
framebuffer contents. This means this does not really work yet.

Signed-off-by: Guillaume Clement <gclement@baobob.org>
desco: Allow to run desco outside the host more easily

Now we can either find resources in the current directory, or from a
specified environment variable.

Signed-off-by: Guillaume Clement <gclement@baobob.org>