Mockup of the new package os interface (incomplete and non-functioning)

core/os/os2/errors_windows.odin

@@ -0,0 +1,14 @@
+//+private
+package os2
+
+import win32 "core:sys/windows"
+
+_error_string :: proc(errno: i32) -> string {
+	e := win32.DWORD(errno);
+	if e == 0 {
+		return "";
+	}
+	// TODO(bill): _error_string for windows
+	// FormatMessageW
+	return "";
+}