Fix incorrect cast to ssize_t.
Fix incorrect cast to ssize_t.

gcc 4.2.1 warns about a possible incorrect cast to ssize_t when comparing against refcount, which is of type size_t. signed vs unsigned comparison.

Sinc warnings are treated as errors (as in the autoconf project) this would cause a compile error.

OlehKulykov/jansson,markalanj/jansson,bstarynk/jansson,attie/jansson,Mephistophiles/jansson,npmccallum/jansson,simonfojtu/FireSight,firepick-delta/FireSight,OlehKulykov/jansson,npmccallum/jansson,rogerz/jansson,rogerz/jansson,firepick1/jansson,chrullrich/jansson,attie/jansson,wirebirdlabs/featherweight-jansson,liu3tao/jansson,Mephistophiles/jansson,simonfojtu/FireSight,rogerz/jansson,firepick1/jansson,akheron/jansson,AmesianX/jansson,firepick1/FireSight,firepick-delta/FireSight,slackner/jansson,akheron/jansson,firepick1/FireSight,chrullrich/jansson,Vorne/jansson,Vorne/jansson,slackner/jansson,markalanj/jansson,simonfojtu/FireSight,akheron/jansson,firepick-delta/FireSight,bstarynk/jansson,bstarynk/jansson,liu3tao/jansson,firepick1/FireSight,AmesianX/jansson,markalanj/jansson,firepick1/jansson,wirebirdlabs/featherweight-jansson,rogerz/jansson