Cleanup Makefiles

src/backend/optimizer/path/Makefile

src/backend/optimizer/path/joinpath.c

src/backend/optimizer/plan/Makefile

src/backend/optimizer/plan/createplan.c

src/backend/optimizer/plan/initsplan.c

src/backend/optimizer/plan/planmain.c

src/backend/optimizer/plan/planner.c

src/backend/optimizer/plan/setrefs.c

src/backend/optimizer/prep/Makefile

src/backend/optimizer/prep/prepqual.c

src/backend/optimizer/prep/prepunion.c

src/backend/optimizer/util/Makefile

src/backend/optimizer/util/indexnode.c

src/backend/optimizer/util/internal.c

src/backend/optimizer/util/ordering.c

src/backend/optimizer/util/var.c