Add MariaDB to CI configuration

[tabarnhack]

According to #257, MariaDB has been added to CI configuration. The minimal version taken of MariaDB is 10.2 as the 10.1 has an EOL on October 2020, thus this version is obsolete.

[AlekSi]

@tabarnhack But those changes are not enough to actually test agains MariaDB – you have to change Makefile too

[tabarnhack]

Indeed, I did not read the codebase enough to understand where the tests was made. I've made the changes. It should be good now.

[codecov[bot]]

Codecov Report

Merging #307 (752c63f) into main (ba989a9) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #307   +/-   ##
=======================================
  Coverage   68.57%   68.57%           
=======================================
  Files          20       20           
  Lines        1715     1715           
=======================================
  Hits         1176     1176           
  Misses        484      484           
  Partials       55       55           

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