Author: Shamim Rezaie
MDL-43189 core: Validate db prefix during installation
http://git.moodle.org/gw?p=moodle.git;a=commit;h=f41a30229eced1b84eef3a2b3475272153d4398f
http://github.com/moodle/moodle/commit/f41a30229eced1b84eef3a2b3475272153d4398f
+ 3.7 en [invaliddbprefix,core_install]