npgsql - Npgsql2: need to read in chunks so the socket doesn't run out

Log Message:
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need to read in chunks so the socket doesn't run out of memory in recv the network stream doesn't prevent this and downloading a large bytea will throw an IOException with an error code of 10055 (WSAENOBUFS)
This is a fix for bug reported in 1005719.

Modified Files:
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Npgsql2/src/Npgsql:
PGUtil.cs (r1.10 -> r1.11)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/src/Npgsql/PGUtil.cs?r1=1.10&r2=1.11)