IO split patch review

[ghost]

The IO split draft currently at jacksonh/manos@791a0e6d88dd51689a4f should be reviewed before we merge it into master. All major issues i encountered during my tests are fixed, and benchmarks show little to no performance degradation. Explanation for "little": the managed IO code didn't guarantee some things the libev IO code did guarantee, and as a consequence, http transaction and managed IO did not get along too well. That is fixed with a rather nasty workaround for time being.

Major points of the changeset:

• it is now possible to use the IO core of manos without having to link the http part
• we now have a compile-time flag that forces Manos.IO to the managed implementation, so the IO core is also embeddable into pretty much everything CLR
• multiple event loops, now named contexts, are possible without any imposed binding to threads
• factories for file streams and sockets per context, the resulting objects are then bound to that context and process events through it's event loop
• prepare, check, idle and async watchers per context for whatever you might want to do with them

any feedback is welcome.

[ghost]

I guess non-objection is a silent nod. If that's the case, I'll simply merge soon.

[ghost]

Merged.