Ensure scriptlet logging information make it to destination

Avoid race conditions between isolated world-side broadcast channel
and main-side broadcast channel, so as to not lose logging
information if the isolated world-side is not yet ready to
receive through its broadcast channel.

Additionally, added new scriptlet: `trusted-replace-argument`.

[...]##+js(trusted-replace-argument, fn, argpos, argval [,condition, pattern])

Where:

- `fn` is the function we want to proxy through an `apply` handler.
  This can also be a class, in which case the scriptlet will proxy
  through `construct` handler. At the moment, `fn` must exist at the
  time the scriptlet executes.

- `argpos` is the 0-based position of the argument we want to change

- `argval` is the value we want to have for the argument -- the value
  is interpreted the same way the value for `set-constant` is
  interpreted.

- `condition, pattern` is a vararg which tells the scriptlet to act
  only if `pattern` is found in the argument to overwrite.

Example of usage:

    alliptvlinks.com##+js(trusted-replace-argument, MutationObserver, 0, noopFunc)

Author: gorhill