utf8.c: Faster latin1 upper/title casing

utf8.c: Faster latin1 upper/title casing

This creates a new function to handle upper/title casing code points in
the latin1 range, and avoids using a swash to compute the case.  This is
because the correct values are compiled-in.

And it calls this function when appropriate for both title and upper
casing, in both utf8 and uni forms,

Unlike the similar function for lower casing, it may make sense for this function to be
called from outside utf8.c, but inside the core, so it is not static,
but its name begins with an underscore.