pgsql: Allow usage of huge maintenance_work_mem for GIN build.

Allow usage of huge maintenance_work_mem for GIN build.

Currently, in-memory posting list during GIN build process is limited 1GB
because of using repalloc. The patch replaces call of repalloc to repalloc_huge.
It increases limit of posting list from 180 millions
(1GB / sizeof(ItemPointerData)) to 4 billions limited by maxcount/count fields
in GinEntryAccumulator and subsequent calls. Check added.

Also, fix accounting of allocatedMemory during build to prevent integer
overflow with maintenance_work_mem > 4GB.

Robert Abraham <robert(dot)abraham86(at)googlemail(dot)com> with additions by me

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/30bb26b5e04cff911db960801e32e5f57045eb61

Modified Files
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src/backend/access/gin/ginbulk.c | 10 +++++++++-
src/backend/access/gin/ginfast.c | 2 +-
src/backend/access/gin/gininsert.c | 2 +-
src/include/access/gin_private.h | 2 +-
4 files changed, 12 insertions(+), 4 deletions(-)