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

[Gudjon I. Gudjonsson]

Hi Sven

You are right. I did compile the file in a normal environment with elyxer installed, sorry.
But I cannot compile the package (version 27) after I uninstall elyxer. Lyx fails without any 
proper error message.
The problem seems to be in the new documentation. If I copy the documentation from ngspice-26 to
ngspice-27, build-indep works.
ngspice-26, manual.lyx is made with lyx 2.0 and lyx format 413
ngspice-27, manual.lyx is made with lyx 2.1 and lyx format 474

Do you have any idea on how to remove this elyxer dependency from manual.lyx?

Regards
Gudjon