Fix czar link/load bug with log4cxx

On Ubuntu 14.04, the czar would fall over at load time with an unresolved
sym (for typeinfo for log4cxx::helpers::ObjectPtrBase) while loading the
css python wrapper shared lib.  It seems the linker was tripping up chasing
transitive dependencies through the shared libs.

This cl tweaks core/modules/Sconscript to provide additional explicit link libs 
to "shmod" shared modules to hint the linker.