Makefile cleanup after reorganization

src/backend/access/heap/Makefile

src/backend/access/transam/Makefile

src/backend/bootstrap/Makefile

src/backend/lib/Makefile

src/backend/main/Makefile

src/backend/optimizer/path/Makefile

src/backend/optimizer/plan/Makefile

src/backend/optimizer/prep/Makefile

src/backend/parser/Makefile

src/backend/port/BSD44_derived/Makefile

src/backend/port/aix/Makefile

src/backend/port/alpha/Makefile

src/backend/port/bsdi/Makefile

src/backend/port/dgux/Makefile

src/backend/port/hpux/Makefile

src/backend/port/i386_solaris/Makefile

src/backend/port/irix5/Makefile

src/backend/port/linux/Makefile

src/backend/port/sparc/Makefile

src/backend/port/sparc_solaris/Makefile