Use Typed Arrays for the Websock receive queue

**This commit removes Base64 (and Flash) support**

This commit converts websock.js to used Typed Arrays for the
receive queue (and tweaks rfb.js to ensure that it continues
to function, since only Firefox implements
`%TypedArray%.prototype.slice`).  Base64 support was removed
to simplify code paths, and pave the way for using Typed Arrays
for the send queue as well.

This provides two advantages: first, we allocate a buffer ahead
of time, meaning the browser doesn't have to do any work dynamically
increasing the receive queue size.  Secondly, we are now able to pass
around Typed Array Views (e.g. `Uint8Array`), which are lightweight, and
don't involve copying.

The downside is that we initially allocate more memory -- we currently
start out with 4 MiB, and then automatically double when it looks like
the amount unused is getting to small.

The commit also explicitly adds a check to the compacting logic that
avoids calling the copy functions if `_rQlen === _rQi`.

docs/notes

@@ -1,21 +1,3 @@
-Some implementation notes:
-
-There is an included flash object (web-socket-js) that is used to
-emulate websocket support on browsers without websocket support
-(currently only Chrome has WebSocket support).
-
-Javascript doesn't have a bytearray type, so what you get out of
-a WebSocket object is just Javascript strings.  Javascript has UTF-16
-unicode strings and anything sent through the WebSocket gets converted
-to UTF-8 and vice-versa. So, one additional (and necessary) function
-of websockify is base64 encoding/decoding what is sent to/from the
-browser.
-
-Building web-socket-js emulator:
-
-cd include/web-socket-js/flash-src
-mxmlc -static-link-runtime-shared-libraries WebSocketMain.as
-
 Rebuilding inflator.js
 
 - Download pako from npm