amused-web: allocate lazily the (double) buffer for chunking

amused-web: parse POST data in bufio' rbuf Add a proper upper limit (4096 seems enough for now) and safely NUL-terminate the rbuf. The idea is to later drop the clt->buf static buffer and allocate it on demand only when we need to do (http) chunking.

amused-web: add websocket support; send forms via js if available This allows amused-web to stay in sync using websockets (much like existing amused clients watch `amused monitor') and sends the forms in the background to avoid refreshing the page. Still missing is reopening the websocket, maybe blocking the UI in that case and showing the progress.

amused-web: set http.[ch] as public domain code

amused-web: rework client handling on top of bufio / ev

use Transfer-Encoding: chunked only on HTTP/1.1 w3m (HTTP/1.0) doesn't seem to like it.

add amused-web, a web interface to control amused It's a first stab at it, some planned features (like the search) are missing but the basic ones work. It's not hooked in the main build yet.