BUG #1936: Read-only transactions ignored in COPY

The following bug has been logged online:

Bug reference:      1936
Logged by:          Alon Goldshuv
Email address:      agoldshuv@greenplum.com
PostgreSQL version: 8 (Current Dev)
Operating system:   any
Description:        Read-only transactions ignored in COPY
Details:

In the folllowing check (copy.c:DoCopy() ), i *think* that the check for the
is_from flag is mistakenly negated. is_from means -> from file to database,
therefore we should check for <XactReadOnly && is_from>, and not
<XactReadOnly && !is_from>

/* check read-only transaction */
if (XactReadOnly && !is_from &&
    !isTempNamespace(RelationGetNamespace(cstate->rel)))
    ereport(ERROR,
            (errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
             errmsg("transaction is read-only")));