Support Win 7

[i486]

I'd like to use this on my Win 7 test machine.

[PragmaTwice]

I think maybe it is not hard, but I have no Windows 7 environment and I currently have no time to build and test it in Windows 7.

But, feel free to submit patches if you want.

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Some suggestions:

You can try to modify value of WIN32_VERSION to 0x0601 here: https://github.com/PragmaTwice/proxinject/blob/master/CMakeLists.txt#L80

and then build the project.