Fix for vacuum and cache use. Fix for BSDI 4.0.

src/backend/access/heap/heapam.c

src/backend/commands/vacuum.c

src/backend/utils/cache/catcache.c

src/backend/utils/cache/inval.c

src/include/utils/inval.h

src/makefiles/Makefile.bsdi

src/makefiles/Makefile.linux

src/makefiles/Makefile.sco