Updated Bangla (Probhat) layout
Hi. The Probhat layout for Bangla — bn(probhat)
/in(ben_probhat)
— used in the project is very old. This is its current form in common use: http://ekushey.org/?page/probhat_layout. The xkb symbol table is particularly missing the AltGr symbols. So I've updated the xkb layout to follow the latest version.
Please review, thanks. cc @svu