- clean up cpp directives.
- stop including rune.h from mklocale.
- stop using _BSD_RUNE_T macro. instead, use int32_t directly in runetype.h.
- move _DEFAULT_INVALID_RUNE to runetype.h.
These were for historical reason on porting rune from FreeBSD,
but it seems that these are no longer reasonable but troublesome
under the current NetBSD build system.
additionally:
- runetype.h -> locale/runetype.h in mklocale, because this might conflict
to FreeBSD's one.