pgsql: Fix full-table-vacuum request mechanism for MultiXactIds

Fix full-table-vacuum request mechanism for MultiXactIds

While autovacuum dutifully launched anti-multixact-wraparound vacuums
when the multixact "age" was reached, the vacuum code was not aware that
it needed to make them be full table vacuums.  As the resulting
partial-table vacuums aren't capable of actually increasing relminmxid,
autovacuum continued to launch anti-wraparound vacuums that didn't have
the intended effect, until age of relfrozenxid caused the vacuum to
finally be a full table one via vacuum_freeze_table_age.

To fix, introduce logic for multixacts similar to that for plain
TransactionIds, using the same GUCs.

Backpatch to 9.3, where permanent MultiXactIds were introduced.

Andres Freund, some cleanup by Álvaro

Branch
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REL9_3_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/f5f92bdc44ffdf577244e0d055825cacd0cdea10

Modified Files
--------------
src/backend/access/transam/multixact.c |   15 ++++++++
src/backend/commands/cluster.c         |   13 ++++---
src/backend/commands/vacuum.c          |   62 +++++++++++++++++++++++---------
src/backend/commands/vacuumlazy.c      |   18 +++++++---
src/include/access/multixact.h         |    2 ++
src/include/commands/vacuum.h          |    5 +--
6 files changed, 87 insertions(+), 28 deletions(-)