lib: luvit: luvit.lua: use OS_BINDING.type()
lib: luvit: luvit.lua: use OS_BINDING.type()

during a refactor luvit_os went away. The consequence is on Windows the ref
count now goes straight to -3 since it misses this if statement. Use
OS_BINDING.type() instead of luvit_os to detect windows.

zhaozg/luvit,DBarney/luvit,luvit/luvit,boundary/luvit,rjeli/luvit,connectFree/lev,sousoux/luvit,bsn069/luvit,sousoux/luvit,bsn069/luvit,rjeli/luvit,sousoux/luvit,zhaozg/luvit,AndrewTsao/luvit,sousoux/luvit,GabrielNicolasAvellaneda/luvit-upstream,boundary/luvit,kaustavha/luvit,bsn069/luvit,boundary/luvit,AndrewTsao/luvit,connectFree/lev,rjeli/luvit,sousoux/luvit,kaustavha/luvit,boundary/luvit,luvit/luvit,GabrielNicolasAvellaneda/luvit-upstream,sousoux/luvit,DBarney/luvit,boundary/luvit,kaustavha/luvit,rjeli/luvit,DBarney/luvit,GabrielNicolasAvellaneda/luvit-upstream,GabrielNicolasAvellaneda/luvit-upstream,AndrewTsao/luvit,boundary/luvit,DBarney/luvit