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.
The current width was tested after the index was already
updated to the next character, leading to an off-by-one error,
and the impossibility to select the first character of a string
in textarea.
