pgsql: Add missing library to standalone libpq build on Win32.

Log Message:
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Add missing library to standalone libpq build on Win32.

Hiroshi Saito

Modified Files:
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pgsql/src/interfaces/libpq:
win32.mak (r1.54 -> r1.55)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/win32.mak?r1=1.54&r2=1.55)