unique_ptr::release() has wrong type

[kamahen]

unique_ptr::release() should be something like this:

inline T* release() throw()
{
    T* get_px = px;
    px = nullptr;
    return get_px;
}

googletest/googletest/include/gtest/internal/gtest-port.h gets this right.

Also, there's no test case for release().

(There's also a private release() const, whose comment I don't understand; presumably it should also return the value? But it doesn't seem to be used anywhere.)