Socket abstractions

~~Rename all lua_ to ncat_lua to avoid name collisions.~~
- ~~Extra points if it's done as a clever Perl one-liner. :>~~
local make_function = function(), to get rid of the ugly function_self thing.
ret[m] = function(self, ...) return table.unpack({self.super[m](self.super, ...)}) end
- return self.super[m](self.super, ...)
- perhaps just copy the parent's function? explore it.
Look into ways of making recv() call self.super:recv() only once, not running send() (and send() not running recv() until it gets figured out).
Add way more comments into the coroutine code.
Add some error handling for nil returned by the socket methods.
What happens if we call recv() inside of recv()?
- Idea for a solution: set a flag before calling the recv() at the very bottom and return nil if we're already in recv.
- 19:25:31 yyzfp$ Lua filters should not be scheduling their own next reads.
- 19:30:34 yyzfp$ Also check nse_yield.
Have a look at copas/kepler and luasocket.
- Also see: http://lua-users.org/wiki/FiltersSourcesAndSinks http://w3.impa.br/~diego/software/luasocket/ltn12.html

Not a priority

recv() - add the numbytes argument to that would let you control how much data is read
connect() - pass the key to the connections[] global array as an argument
close() - try to close cleanly
Find a way to rewrite nls->in_send
Make lowest-level socket an userdata.
Detect when user calls coroutine.resume().
- nse_main.lua:988
See if I can get away without saving the coroutines by not using the main thread in recv handler.