pgsql: Avoid allocations in critical sections.

Avoid allocations in critical sections.

If a palloc in a critical section fails, it becomes a PANIC.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/877b088785b178c50e7976d86c82dfafa4031792

Modified Files
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src/backend/access/nbtree/nbtinsert.c   |   55 ++++++++++++++++---------------
src/backend/access/spgist/spgdoinsert.c |    8 ++---
src/backend/access/transam/xlog.c       |   22 +++++--------
src/backend/storage/page/bufpage.c      |   21 +++++-------
4 files changed, 49 insertions(+), 57 deletions(-)