pgsql: Fix failure to mark init buffers as BM_PERMANENT.

Fix failure to mark init buffers as BM_PERMANENT.

This could result in corruption of the init fork of an unlogged index
if the ambuildempty routine for that index used shared buffers to
create the init fork, which was true for gin, gist, and hash indexes.

Patch by me, based on an earlier patch by Michael Paquier, who also
reviewed this one. This also incorporates an idea from Artur
Zakirov.

Discussion: http://postgr.es/m/CACYUyc8yccE4xfxhqxfh_Mh38j7dRFuxfaK1p6dSNAEUakxUyQ@mail.gmail.com

Branch
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REL9_3_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/6bd7816e766abd6c10db16ed0af93a512b1a662d

Modified Files
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src/backend/storage/buffer/bufmgr.c | 7 ++++++-
src/include/storage/buf_internals.h | 2 +-
2 files changed, 7 insertions(+), 2 deletions(-)