We had switched hash-password, but not set-password.

Suggested by Stefan Vink of Radically Open Security.

Now that we limit the number of concurrent password hashing
operations, it is safe to use an algorithm that uses a fait
amount of memory.  We use strength 8, which is below the recommended
default, in order to keep password hashing time below 25ms.

This avoids running out of memory when doing too many BCrypt
operations at the same time.

Safari doesn't implement filtered drawing on HTML canvas,
it silently ignores the "filter" property of Context2D.
We implement our own blurring by scaling the background down
and then back up.

Also close the stream when we leave.

This hasn't been needed for a long time.

For now, we only reject usernames that might lead to path traversal.
Thanks to Stefan Vinck of Radically Open Security.

We used to only forbid them under Windows.

Thanks to Stefan Vinck of Radically Open Security.

Thanks to Stefan Vinck of Radically Open Security.

Thanks to Baptiste Daroussin.

We were correctly clearing the chat on the server side, but
we were leaving stray entries in the client.

Thanks to J.-J. Sarton.

Thanks to J.-J. Sarton.

This fixes an issue with negotiation of RTCP feedback.

Since we now make HTTP requests from addFilter, this makes
startup slightly faster.