Add Bépo 1.1rc2 version as normalized by AFNOR

In April 2019, AFNOR, the French normalization organization, published the NF Z71-300 norm to promote two ergonomic keyboard layouts for the French language. AFNOR released a press report (in French) presenting the new norm here. The first proposed layout is an update to the de facto standard AZERTY keyboard, and was already integrated to xkeyboard-config in a previous merge request.

The second layout is a new version of the Bépo keyboard layout, for which an older version is already available in xkb. AFNOR normalized the 1.1 version of this norm, and to this day, its last iteration is the 1.1rc2 version. The details of this layout and its changes from the 1.0 Bépo layout are presented here.

This merge request does not replace the old bepo layout, as the new version introduces a few breaking changes to the keymap. Instead, it adds a new layout called bepo_afnor, which simply implements the xkb configuration available on the Bépo official website.

Caveat: The base map and most features of the layout work correctly, but a complete implementation of the Bépo 1.1 layout requires defining the behavior of new dead keys (extended latin, scientific, exponents and indices). This requires an additional contribution to libx11, which has been proposed for merging. In the meantime, to be able to use the new dead keys, Bépo users need to edit their ~/.XCompose.