When the fetch of asynchronous javascript scripts completed the
completion of html rendering was not processed leaving the state
machine waiting forever.
This changes the LOG macro to be varadic removing the need for all
callsites to have double bracketing and allows for future improvement
on how we use the logging macros.
The callsites were changed with coccinelle and the changes checked by
hand. Compile tested for several frontends but not all.
A formatting annotation has also been added which allows the compiler
to check the parameters and types passed to the logging.
The html content script handling needs to invalidate its JavaScript
context when the browsing context (browser_window) containing it is
either closed or the content fetch is aborted (stopped)
Previously the invalidation was only done on browser_window close
which resulted in use after free crashes because of the now invalid
JavaScript context.
