Correctly handle paths containing whitespace character

[fzhinkin]

Fixes #246

[05nelsonm]

I was incorrect in terms of java.io.File parity. null should not be returned when encountering a parent return value of .

My own tests were not removing the trailing slashes when instantiating things.

./some_path should always return . for a parent

EDIT: So, the issue seems to be with Path not stripping trailing system separators from the end of the string when instantiating it for Native.

Java behavior:

println("'${File("path////")}'")
// 'path'

kotlinx-io behavior (Native):

println("'${Path("path////")}'")
// 'path////'

Need something like

private inline fun String.removeTrailingSlashes(): String {
    var l = length

    while (l > 0) {
        if (this[l - 1] == SystemPathSeparator) {
            l--
        } else {
            break
        }
    }

    return when (l) {
        0 -> ""
        length -> this
        else -> substring(0, l)
    }
}