pgsql: Add new function log_newpage_buffer.

Add new function log_newpage_buffer.

When I implemented the ginbuildempty() function as part of
implementing unlogged tables, I falsified the note in the header
comment for log_newpage. Although we could fix that up by changing
the comment, it seems cleaner to add a new function which is
specifically intended to handle this case. So do that.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/6cd015bea38b8a59feb84bf238a880a3b503cf5f

Modified Files
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src/backend/access/gin/gininsert.c | 12 ++------
src/backend/access/heap/heapam.c | 54 +++++++++++++++++++++++++++++++++--
src/include/access/heapam.h | 1 +
3 files changed, 54 insertions(+), 13 deletions(-)