Code review for MD5 authorization patch. Clean up some breakage

doc/src/sgml/client-auth.sgml

doc/src/sgml/protocol.sgml

doc/src/sgml/ref/alter_user.sgml

doc/src/sgml/ref/create_user.sgml

doc/src/sgml/runtime.sgml

src/backend/libpq/auth.c

src/backend/libpq/crypt.c

src/backend/libpq/hba.c

src/backend/libpq/md5.c

src/backend/postmaster/postmaster.c

src/include/libpq/hba.h

src/interfaces/libpq/Makefile

src/interfaces/libpq/fe-auth.c