- Regression test for missing bounds check in MemIo::seek()
- Add bounds check to MemIo::seek(), this fixes CVE-2019-13504
(cherry picked from commit bd0afe0390439b2c424d881c8c6eb0c5624e31d9)
Additional fixes for 0.27:
- Add fix for the linux variant of MemIo::seek
- Change type of variable from unsigned to signed
