Error message editing in backend/utils (except /adt).

doc/src/sgml/xfunc.sgml

src/backend/utils/cache/catcache.c

src/backend/utils/cache/inval.c

src/backend/utils/cache/lsyscache.c

src/backend/utils/cache/relcache.c

src/backend/utils/cache/syscache.c

src/backend/utils/fmgr/README

src/backend/utils/fmgr/fmgr.c

src/backend/utils/fmgr/funcapi.c

src/backend/utils/hash/dynahash.c

src/backend/utils/init/findbe.c

src/backend/utils/init/miscinit.c

src/backend/utils/init/postinit.c

src/backend/utils/mb/conv.c

.../conversion_procs/utf8_and_iso8859_1/utf8_and_iso8859_1.c

src/backend/utils/mb/encnames.c

src/backend/utils/mb/mbutils.c

src/backend/utils/misc/database.c

src/backend/utils/misc/guc-file.l

src/backend/utils/misc/guc.c