MFH: r398630

• Update to 1.3.13
• Take maintainership

PR: 203545
Submitted by: takefu@airport.fm
Approved by: ports-secteam (erwin)
Security: https://tls.mbed.org/tech-updates/releases/polarssl-1.2.15-and-mbedtls-1.3.12-released
Security: https://tls.mbed.org/tech-updates/releases/mbedtls-2.1.1-and-1.3.13-and-polarssl-1.2.16-released