Bug#882699: ngspice: Remove build dependency on elyxer to allow for the elyxer removal from Debian

[Gudjon I. Gudjonsson]

Hi Sven

> 
> So if you do not use LyX for interactive document writing just rm -r ~/.lyx in your
> build environment and it should reconfigure on the next invocation.
> 
> Another possibility would be that lyx fails to import and convert the manual to the
> current LyX 2.2.x document format.
> Which repo are you building from right now? I'd like to try it out just to see what
> happens.
> 
I tried all options but without success.
But the only thing that works in both sbuild and normal environment is to add dependency 
on elyxer. 

Latest changes are pushed to git and I uploaded the package to my private repository:

deb-src [allow-insecure=yes allow-downgrade-to-insecure=yes] http://gudjon.org/debian/ source/
deb [allow-insecure=yes allow-downgrade-to-insecure=yes] http://gudjon.org/debian/ amd64/

Can you please take a look?

Merry Christmash
Gudjon