tor/changes/ifdef-winnt

  o Build changes:
    - On Windows, we now define the _WIN32_WINNT macros only if they
      are not already defined. This lets the person building Tor decide,
      if they want, to require a later version of Windows.
Make WIN32_WINNT defines conditional Requested by Gisle Vanem on tor-dev. I'm not quite sure this is the right solution, but it's probably harmless. 2011-07-15 16:03:59 +02:00			`o Build changes:`
			`- On Windows, we now define the _WIN32_WINNT macros only if they`
			`are not already defined. This lets the person building Tor decide,`
			`if they want, to require a later version of Windows.`