pgsql: Improve behavior of concurrent ALTER .. SET SCHEMA.

Improve behavior of concurrent ALTER <relation> .. SET SCHEMA.

If the referrent of a name changes while we're waiting for the lock,
we must recheck permissons.  We also now check the relkind before
locking, since it's easy to do that long the way.

Patch by me; review by Noah Misch.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/1da5c119594e4fb07fb6a2c57f66642fa5e966fb

Modified Files
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src/backend/commands/alter.c     |    1 -
src/backend/commands/tablecmds.c |  113 +++++++++++++++++++++++--------------
2 files changed, 70 insertions(+), 44 deletions(-)