Add open and close.
Add open and close.

Generalise get_rlimit_const to lookup_symbol, and use it for open
flags.

Add a FIXME.

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