[Bug 2125153] ibus does not support special Arabic compose sequences

https://bugzilla.redhat.com/show_bug.cgi?id=2125153

--- Comment #2 from Mike FABIAN  ---
The problem in ibus seems to be something different, sequences not starting
with Multi_key and not with dead keys do work.
It is not the length of the sequence either, even sequences of length 1 work
**if** they are written in ~/.XCompose

So adding a ~/.XCompose like this makes typing the `b` key with the Arabic
keyboard layout do the right thing:

$ cat ~/.XCompose
include "/%L"
<UFEFB> :   "لا" # ARABIC LIGATURE LAM WITH ALEF
<U263A> : "single char compose sequence worked"
$

But that sequence is already defined in the system wide compose file:

$ grep '^<UFEFB>' /usr/share/X11/locale/en_US.UTF-8/Compose
<UFEFB> :   "لا" # ARABIC LIGATURE LAM WITH ALEF

So it should work without having to add a ~/.XCompose file, but it doesn't.