Session_label constructor now takes a bare string rather than a
serialized argument buffer.
Replace all instances of previous constructor with 'label_from_args'
function.
Issue #1787
Notify client initially to enforce a client-side ROM update. Otherwise,
a server-side ROM update between session creation and signal-handler
registration would go unnoticed.
Issue #1788
This patch moves the formerly internal classes of the report-ROM service
to the public location os/include/report_rom/ so that they can be reused
by other components such as the upcoming clipboard.
