pgsql: Ensure an index that uses a whole-row Var still depends on its t

Ensure an index that uses a whole-row Var still depends on its table.

We failed to record any dependency on the underlying table for an index
declared like "create index i on t (foo(t.*))". This would create trouble
if the table were dropped without previously dropping the index. To fix,
simplify some overly-cute code in index_create(), accepting the possibility
that sometimes the whole-table dependency will be redundant. Also document
this hazard in dependency.c. Per report from Kevin Grittner.

In passing, prevent a core dump in pg_get_indexdef() if the index's table
can't be found. I came across this while experimenting with Kevin's
example. Not sure it's a real issue when the catalogs aren't corrupt, but
might as well be cautious.

Back-patch to all supported versions.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=9f376e146b2f1fe1bc4d07380f2a047d5c375581

Modified Files
--------------
src/backend/catalog/dependency.c | 15 ++++++++++++++-
src/backend/catalog/index.c | 15 +++++----------
src/backend/utils/adt/ruleutils.c | 24 +++++++++++++++++++++---
3 files changed, 40 insertions(+), 14 deletions(-)