The netsurf core is driven from numerous operation tables most of
which are now set through a common netsurf_register() interface. The
font and plotting interfaces are currently separate and unlike all the
other operation tables are modified for differing contexts.
This change moves the font operations alongside all the other
operations table and remove unnecessary interaction with the renderers
font internals. Further this also removes the need for css internals
to be visible in frontends.
Keypresses now go via content interface.
Contents don't shove the selection object into browser windows any more.
Contents report selection existence by sending message.
HTML content keeps track of where selections in it exist.
Contents report whether they have input focus via caret setting msg.
Caret can be hidden (can still input/paste) or removed.
Consolidate textarea selection handling.
Make textarea report its selection status changes to client.
Various textarea fixes.
Changed how we decide when to clear selections, and give focus.
