Bug#337688: xkb files from xlibs >= 6.8.99 need xkb files from xlibs-data >= 6.8.99

[Robert Bihlmeyer <robbe@orcus.priv.at>]

Package: xlibs
Version: 6.8.99.901.dfsg.1-1
Severity: normal
Tags: experimental

xlibs ships with /etc/X11/xkb/compat/basic (used by the default server config),
which relies on /etc/X11/xkb/compat/ledcaps. This file is not in the same
package but in xlibs-data (on purpose or by mistake?). Since old versions of
xlibs-data don't have ledcaps, the dependency of xlibs on xlibs-data needs to
be versioned.

Otherwise it is possible to install a new xlibs with an old xlibs-data
resulting in non-working xkb with the following diagnostics:

The XKEYBOARD keymap compiler (xkbcomp) reports:
> Error:            Can't find file "ledcaps" for compat include
>                   Exiting
>                   Abandoning compatibility map "basic"
>                   Abandoning compatibility map "complete"
>                   Abandoning compatibility map "default"

This bug may be related to 337637.