pgsql: Make the win32 putenv() override update *all* present versions of

Log Message:
-----------
Make the win32 putenv() override update *all* present versions of the
MSVCRxx runtime, not just the current + Visual Studio 6 (MSVCRT). Clearly
there can be an almost unlimited number of runtimes loaded at the same
time.

Per report from Hiroshi Inoue

Modified Files:
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    pgsql/src/port:
        win32env.c (r1.5 -> r1.6)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/port/win32env.c?r1=1.5&r2=1.6)