Add a few more DTrace probes to the backend.

src/backend/Makefile

src/backend/access/transam/clog.c

src/backend/access/transam/multixact.c

src/backend/access/transam/subtrans.c

src/backend/access/transam/twophase.c

src/backend/postmaster/pgstat.c

src/backend/storage/buffer/bufmgr.c

src/backend/storage/lmgr/deadlock.c

src/backend/storage/lmgr/lock.c

src/backend/storage/lmgr/lwlock.c

src/backend/tcop/postgres.c

src/backend/tcop/pquery.c

src/backend/utils/Gen_dummy_probes.sed

src/backend/utils/Makefile

src/backend/utils/probes.d

src/backend/utils/sort/tuplesort.c