Fix bug #7724071 ImageView drawable is not loaded correctly when changing Locale

aapt is not generating the correct CONFIG_LAYOUTDIR bit when a Drawable has a
LTR and RTL version. It was generating instead the wrong CONFIG_SCREEN_LAYOUT bit.

This was linked to the fact that the layout direction bits are contained into the
screen layout bit.

So now make sure that we are generating the correct CONFIG_LAYOUTDIR bit.

Change-Id: If17c84d31e6c128721ed97ee6711660b131bf941