[arch-general] Move from libjpeg-turbo to mozjpeg

[N30N]

> 	-1.
> 
> 	mozjpeg offers slightly improved compression at the cost of up to
> x10 increase in compression time (*). It may be something to
> consider later if they manage to improve the speed although they
> expect that it will always remain slower than libjpeg-turbo.

As I quoted before the "defaults are the same as for libjpeg-turbo". The 
optimisations are enabled for cjpeg and jpegtran but there's a 
"-fastcrush" option to disable the progressive scan optimization.