some PIFile functionality

PIBinaryLog::close fix

libs/main/io_devices/pidir.cpp

@@ -160,6 +160,16 @@ PIDir & PIDir::cleanPath() {
 PIString PIDir::relative(const PIString & path) const {
 	PIDir td(path);
 	PIStringList dl(absolutePath().split(separator)), pl(td.absolutePath().split(separator)), rl;
+	auto checkPath = [](PIStringList & path) {
+		if (path.isEmpty()) return;
+		if (path[0].size() >= 2) {
+			if (path[0][0].isAlpha() && path[0][1] == ':') {
+				path[0][0] = path[0][0].toUpper();
+			}
+		}
+	};
+	checkPath(dl);
+	checkPath(pl);
 	// piCout << pl << "rel to" << dl;
 	while (!dl.isEmpty() && !pl.isEmpty()) {
 		if (dl.front() != pl.front()) break;