function reDirnameWindows() {
	return /^((?:[a-zA-Z]:|[\\\/]{2}[^\\\/]+[\\\/]+[^\\\/]+|)(?:[\\\/]|)(?:[\s\S]*?))(?:[\\\/]+?|)(?:(?:\.{1,2}|[^\\\/]+?|)(?:\.[^.\/\\]*|))(?:[\\\/]*)$/; // eslint-disable-line no-useless-escape
}
Returns a regular expression to capture a Windows path dirname.

@returns {RegExp} regular expression

@example
var RE_DIRNAME_WINDOWS = reDirnameWindows();
var dir = RE_DIRNAME_WINDOWS.exec( 'foo\\bar\\index.js' )[ 1 ];
// returns 'foo\bar'