pgsql: Document that && can be used to search arrays.

Document that && can be used to search arrays.

Also, add some cross-links to the indexing documentation, so it's easier
to notice that && and other array operators have index support.

Ryan Kelly, edited by me.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/6ef5baf8b1cb609218b2fafb378b3f190a6f90f9

Modified Files
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doc/src/sgml/array.sgml |   14 ++++++++++++++
doc/src/sgml/func.sgml  |    3 ++-
2 files changed, 16 insertions(+), 1 deletions(-)