pgsql: Make sure that GIN fast-insert and regular code paths enforce the

Log Message:
-----------
Make sure that GIN fast-insert and regular code paths enforce the same
tuple size limit.  Improve the error message for index-tuple-too-large
so that it includes the actual size, the limit, and the index name.
Sync with the btree occurrences of the same error.

Back-patch to 8.4 because it appears that the out-of-sync problem
is occurring in the field.

Teodor and Tom

Modified Files:
--------------
    pgsql/src/backend/access/gin:
        ginentrypage.c (r1.21 -> r1.22)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gin/ginentrypage.c?r1=1.21&r2=1.22)
        ginfast.c (r1.4 -> r1.5)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gin/ginfast.c?r1=1.4&r2=1.5)
        gininsert.c (r1.23 -> r1.24)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gin/gininsert.c?r1=1.23&r2=1.24)
        ginvacuum.c (r1.30 -> r1.31)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gin/ginvacuum.c?r1=1.30&r2=1.31)
    pgsql/src/backend/access/nbtree:
        nbtinsert.c (r1.173 -> r1.174)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtinsert.c?r1=1.173&r2=1.174)
        nbtsort.c (r1.119 -> r1.120)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtsort.c?r1=1.119&r2=1.120)
    pgsql/src/include/access:
        gin.h (r1.34 -> r1.35)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/access/gin.h?r1=1.34&r2=1.35)