Add explicit dependency on CFFI to provide a call to CFFI-SYS:NATIVE-NAMESTRING in decorators.lisp for LispWorks.

On CL implementations other than LispWorks, CFFI is already loaded as a
dependency of CL+SSL providing SSL support in HUNCHENTOOT.  This never happens
on LispWorks as it has a native SSL implementation used by HUNCHENTOOT.
Merge pull request #20 from ska80/dev

Add explicit dependency on CFFI to provide a call to CFFI-SYS:NATIVE-NAM...