Bug#941804: exim4: remote_smtp_smarthost transport does not set DKIM variables

[Larry Doolittle]

Control:
found 941804 4.94.2-7+deb11u1 
found 941804 4.96-15+deb12u2
found 941804 4.97~RC1-2
severity 941804 normal
thanks

This exim4 bug has taken on increased importance now that gmail requires DKIM
on all (?) incoming messages.
I checked and can confirm its presence in the three versions above,
as currently used in bullseye, bookworm, and trixie.

 - Larry