Performance improvements.

Feedback from LuaJIT mailing lists and Mike Pall means performance improvements from everyone.
Closures avoided as this aborts tracing.
Static buffers are used when possible.
All IOStream callback functions now takes one additional arguments, arg, which is used as first parameter to the callback. This means self references can be provided and closures can be avoided if wanted.
AsyncHTTPClient timeout fixed. (Fixes the GFW of China case)
AsyncHTTPClient connect failures added.
Added new low level buffer class.

Thanks for all pointers.