Add a 'matchchars' option to set the character pairs that % looks for.
Traditionally this was []{}() but someone added <> to nvi - probably
for editing html, but it is a pain for C. :set matchars=[]{}() will
restore the traditional behaviour.
If the 'open' and 'close' characters are the same (eg "" or '') then % will
alternate forwards and backwards searches.
Use common code to detect options that must have an even number of characters.
dsl