pgsql: Widen amount-to-flush arguments of FileWriteback and callers.

Widen amount-to-flush arguments of FileWriteback and callers.

It's silly to define these counts as narrower than they might someday
need to be.  Also, I believe that the BLCKSZ * nflush calculation in
mdwriteback was capable of overflowing an int.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/95ef43c4308102d23afa887c9fc28d9977612a2d

Modified Files
--------------
src/backend/storage/file/fd.c   | 14 +++++++-------
src/backend/storage/smgr/md.c   |  9 +++++----
src/backend/storage/smgr/smgr.c |  4 ++--
src/include/storage/fd.h        |  2 +-
src/include/storage/smgr.h      |  4 ++--
5 files changed, 17 insertions(+), 16 deletions(-)