Use slicot package instead of embedded copy

Reported by Sylvestre LEDRU

Originally assigned to Paul BIGNIER

In modules/cacsd/src/slicot, we are shipping the source of a thirdparty library.
This should be removed to use it as a thirdparty library (and checked by the configure + thirdparty updated=.

This has been reported here:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=712781