Make test_leaks unit test in core::run work on Windows

[catamorphism]

It's currently ignored on Windows.

[Dretch]

The code in question looks like:

// Regression test for memory leaks
#[ignore(cfg(windows))] // FIXME (#2626)
pub fn test_leaks() {
    run::run_program("echo", []);
    run::start_program("echo", []);
    run::program_output("echo", []);
}

When I commented-out the ignore and added a #[test] then this test passed on my Windows machine (Mingw32 + 64 bit Windows 7).

So perhaps this particular issue is no more?

[alexcrichton]

Fixed in #5912