Introduce LLCoros::setStackSize(), with a compile-time default value we hope
we never have to use. Make LLAppViewer call it with the value of the new
settings variable CoroutineStackSize as soon as we've read settings files.
(While we're at it, notify interested parties that we've read settings files.)
Give CoroutineStackSize a default value four times the previous default stack
size. Make LLCoros::launch() pass the saved stack size to each new coroutine
instance.
Re-enable lleventcoro integration test. Use LLSDMap() construct rather than
LLSD::insert(), which used to return the modified object but is now void.

made marker file lock use append, not truncate

* Fix mute button.

* Switch mute to use task id.
reviewed with Simon

* Change text of dialog
* Add callback for mute button
reviewed with Richard and Widely.

* Add the newer run time permissions to the viewer
* Filter requested permissions by those the viewer knows about
* Show a dialog indicating unknown permissions were requested and a new viewer
  will be needed to grant them.
reviewed with Simon and Soft

MAINT-2613: remove duplicate entry for "DisablePrecacheDelayAfterTeleporting", and fix a few other llsd validity problems