body_scripts.adp

Added support for streaming HTML + javascript body procs

Previously, the API for bodyscripts (e.g. template::add_body_script,
template::add_event_listener, template::add_body_handler,
template::add_script with the right flags) was not usable for
streaming HTML pages, since the full processing of such scripts was
handled in blank-master.{tcl,adp}, which is not in use for streaming
HTML.

Now the function template::collect_body_scripts was added, which can
be used at arbitrary time to collect the body scripts and translate
those to HTML. This function can be used in streaming mode to output
these function when new HTML chunks become available.