Patch to add Windows 7 support

The attached patch adds support for the Windows 7 beta which we've had
a few reports of incompatibility with. When we startup using pg_ctl on
Windows, we create a job object (a logical grouping of processes on
Windows) to which we apply various security options. One of these
(JOB_OBJECT_UILIMIT_HANDLES) is used to prevent our processes seeing
handles belonging to processes outside of our job, however, when we
run under the service control manager, this causes the postmaster to
exit immeditately for no apparent reason.

I'm not entirely sure what has change in the SCM to cause this yet
(Windows 7 documentation is somewhat thin on the ground at the
moment), but the patch avoids theporblem by only setting
JOB_OBJECT_UILIMIT_HANDLES on earlier OSs.

Tested on CVS head, but should probably be backpatched to 8.3 to avoid
more bug reports.

--
Dave Page
EnterpriseDB UK: http://www.enterprisedb.com