pgsql: Protect against torn pages when deleting GIN list pages.

Protect against torn pages when deleting GIN list pages.

To-be-deleted list pages contain no useful information, as they are being
deleted, but we must still protect the writes from being torn by a crash
after a partial write. To do that, re-initialize the pages on WAL replay.

Jeff Janes caught this with a test program to test partial writes.
Backpatch to all supported versions.

Branch
------
REL9_0_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/8b4efe1f3a4373c9442a710fb01b14c445749d6a

Modified Files
--------------
src/backend/access/gin/ginxlog.c |   28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)