Author: Shamim Rezaie
MDL-43189 core: Validate db prefix during installation
http://git.moodle.org/gw?p=moodle.git;a=commit;h=6def9cd25330f03bd2b6df76011235ab11bd19f3
http://github.com/moodle/moodle/commit/6def9cd25330f03bd2b6df76011235ab11bd19f3
+ 3.8 en [invaliddbprefix,core_install]