pp.c: Call subroutine instead of repeat code

pp.c: Call subroutine instead of repeat code

Now that toLOWER_utf8() and toTITLE_utf8() have the intelligence to skip
going out to swashes for Latin1 code points, it's not so critical to
bypass calling them for these (for speed).  It simplifies things not to
have the intelligence repeated.  There is the additional overhead of two
function calls (minus the branches saved), but these could be avoided if
it comes down to it by making them in-line.