dead or outdated URLs found in win32.h

Hi All,

The following URLs present in src/include/port/win32.h to share the
information on dllimport or dllexport (used in windows) seems to be
either dead/obsolete and i think, they need to be updated.

http://support.microsoft.com/kb/132044 -- dead
http://msdn.microsoft.com/en-us/library/8fskxacy(v=vs.80).aspx -- outdated
http://msdn.microsoft.com/en-us/library/a90k134d(v=vs.80).aspx -- outdated

https://msdn.microsoft.com/en-gb/library/aa489609.aspx -- outdated

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With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com