replace luaL_checkint with luaL_checkinteger
replace luaL_checkint with luaL_checkinteger

No luaL_checkint in Lua 5.3

See https://travis-ci.org/starius/lua-npge/jobs/53188863#L778

starius/lua-npge,starius/lua-npge,starius/lua-npge,npge/lua-npge,npge/lua-npge,npge/lua-npge