src/luv.c: include lua.h
src/luv.c: include lua.h

lua.h must be included before checking for LUA_VERSION_NUM otherwise we
won't get the version and compat-5.3.h will always be needed

Signed-off-by: Fabrice Fontaine <7d88633730b8b85c1516e612893df72eae9cd341@gmail.com>

zhaozg/luv,luvit/luv,luvit/luv,zhaozg/luv