Multi-column GIN indexes. Teodor Sigaev

doc/src/sgml/indices.sgml

doc/src/sgml/ref/create_index.sgml

src/backend/access/gin/ginbulk.c

src/backend/access/gin/ginentrypage.c

src/backend/access/gin/ginget.c

src/backend/access/gin/gininsert.c

src/backend/access/gin/ginscan.c

src/backend/access/gin/ginutil.c

src/backend/access/gin/ginvacuum.c

src/backend/access/gin/ginxlog.c

src/include/access/gin.h

src/include/catalog/catversion.h

src/include/catalog/pg_am.h

src/test/regress/expected/create_index.out

src/test/regress/sql/create_index.sql