package/mariadb: security bump to version 10.3.13

package/mariadb: security bump to version 10.3.13

Release notes:
https://mariadb.com/kb/en/library/mariadb-10313-release-notes/

Changelog:
https://mariadb.com/kb/en/mariadb-10313-changelog/

Fixes the following security vulnerabilities:

CVE-2019-2510 - Vulnerability in the MySQL Server component of Oracle MySQL
(subcomponent: InnoDB). Supported versions that are affected are 5.7.24 and
prior and 8.0.13 and prior. Easily exploitable vulnerability allows high
privileged attacker with network access via multiple protocols to compromise
MySQL Server. Successful attacks of this vulnerability can result in
unauthorized ability to cause a hang or frequently repeatable crash
(complete DOS) of MySQL Server.

CVE-2019-2537 - Vulnerability in the MySQL Server component of Oracle MySQL
(subcomponent: Server: DDL). Supported versions that are affected are 5.6.42
and prior, 5.7.24 and prior and 8.0.13 and prior. Easily exploitable
vulnerability allows high privileged attacker with network access via
multiple protocols to compromise MySQL Server. Successful attacks of this
vulnerability can result in unauthorized ability to cause a hang or
frequently repeatable crash (complete DOS) of MySQL Server.

Note that the hash for README.md changed due to Travis CI and Appveyor CI
updates.

Signed-off-by: Ryan Coe <bluemrp9@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>