pgsql: Call FDW validator functions even when the options list is empty

Call FDW validator functions even when the options list is empty.

This is useful since a validator might want to require certain options
to be provided.  The passed array is an empty text array in this case.

Per suggestion by Laurenz Albe, though this is not quite his patch.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/2e56fa863221d60d8bf8a8b946aaf8ba28ed05e7

Modified Files
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src/backend/commands/foreigncmds.c |   14 ++++++++++++--
1 files changed, 12 insertions(+), 2 deletions(-)