pgsql: neqjoinsel must now pass through collation to eqjoinsel.

neqjoinsel must now pass through collation to eqjoinsel.

Since commit 044c99bc5, eqjoinsel passes the passed-in collation
to any operators it invokes. However, neqjoinsel failed to pass
on whatever collation it got, so that if we invoked a
collation-dependent operator via that code path, we'd get "could not
determine which collation to use for string comparison" or the like.

Per report from Justin Pryzby. Back-patch to v12, like the previous
commit.

Discussion: https://postgr.es/m/20200721191606.GL5748@telsasoft.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/bd0d893aa7aa303d7f344e267a9d3e53b0219491

Modified Files
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src/backend/utils/adt/selfuncs.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)