PREFIX was being set in the Makefile
PR: 13165
Reported by: Oleg V. Volkov <rover@fly.lglobus.ru>
Fix the above problem by patching config.h to use __PREFIX_/__LOCALBASE__
where necessary and then sed s:__PREFIX__:${PREFIX}: etc.
Remove the version number from PLIST, use a PLIST_SUB to make it easier
to upgrade the port.