(Pre)Check for DB reserved words

Shortly, we should check for reserved words as a new precheck step for both core and contributed plug-ins code, more or less as already done by the administrator/developer via /admin/tool/xmldb/index.php?action=view_reserved_words.

Use case: https://moodle.org/mod/forum/discuss.php?d=354485, where I'd suggest to fix the code for the Moodle admin tools.
As a first step, it would be nice to warn the contributors and here is the issue for taking care of it - few feedback for my PR, anyway I could file an issue for that PR too.