Correctly identify Windows hosts when os.name property starts with "win"

[sjmurdoch]

os.indexOf("win") <= 0 will return true if "win" is not found or the string starts with
"win". This will improperly treat platforms which start with "win", e.g. "Windows 7" as if
they are *nix. Testing os.indexOf("win") < 0 will return true only if "win" is not found.

When a Windows host is treated as if it is *nix, the request to load the "c" native library fails,
resulting in:

[error] {file:/C:/<blah>/}<blah>
<blah>/*:dist-unzip: java.lang.UnsatisfiedLinkError: Unable to load library 'c':
 The specified module could not be found.

This appears to be the same problem encountered by this user: https://groups.google.com/d/msg/play-framework/i86yduDeMPU/24A6E8Kk5m0J