refactor: use _helpers.c checkint and optint in curses submodule.
refactor: use _helpers.c checkint and optint in curses submodule.

* ext/posix/curses.c: Use checkint and optint throughout instead
of luaL_checkint & luaL_checknumber and luaL_optint resp.

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

snegovick/luaposix,jimmyharris/luaposix,luaposix/luaposix,snegovick/luaposix,jimmyharris/luaposix,rrthomas/luaposix,zevv/luaposix,ardje/luaposix,rrthomas/luaposix,zevv/luaposix,ardje/luaposix