pgsql: Cap wal_buffers to avoid a server crash when it's set very large

Cap wal_buffers to avoid a server crash when it's set very large.

It must be possible to multiply wal_buffers by XLOG_BLCKSZ without
overflowing int, or calculations in StartupXLOG will go badly wrong
and crash the server.  Avoid that by imposing a maximum value on
wal_buffers.  This will be just under 2GB, assuming the usual value
for XLOG_BLCKSZ.

Josh Berkus, per an analysis by Andrew Gierth.

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/cd52e4a2b945403659219350c4d4c6e6539a1e11

Modified Files
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src/backend/utils/misc/guc.c |    2 +-
1 file changed, 1 insertion(+), 1 deletion(-)