pgsql: WAL-log the extension of a new empty MV heap which is being popu

WAL-log the extension of a new empty MV heap which is being populated.

This page with no tuples is used to distinguish an MV containing a
zero-row resultset of its backing query from an MV which has not
been populated by its backing query.  Unless WAL-logged, recovery
and hot standby don't work correctly with what should be an empty
but scannable materialized view.

Fixes bugs reported by Fujii Masao in testing MVs on hot standby.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/c5bf7a2052c8e7ebbd1ca3986525c3629d7345d1

Modified Files
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src/backend/commands/matview.c |    8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)