WL#4159: Maria 2.5 Performance Update Release

"Maria 2.5 Improved Concurrency Update" alpha

We plan to release a Maria 2.5 alpha intermediate release between 2.0 and 3.0.

This will form a milestone to deliver some of the items regarded important to be 
first done, out of the Maria 3.0 development task list. 

Likely these relate to concurrency improvements.