More README src cleanups.

src/backend/access/heap/README.HOT

src/backend/access/nbtree/README

src/backend/access/transam/README

src/backend/catalog/README

src/backend/executor/README

src/backend/libpq/README.SSL

src/backend/optimizer/README

src/backend/optimizer/plan/README

src/backend/parser/README

src/backend/port/darwin/README

src/backend/port/dynloader/README.dlfcn.aix

src/backend/snowball/README

src/backend/storage/buffer/README

src/backend/storage/lmgr/README

src/backend/storage/smgr/README

src/backend/utils/mb/README

src/backend/utils/resowner/README

src/bin/pg_dump/README

src/bin/pgevent/README

src/interfaces/ecpg/README.dynSQL