Author: Rajesh Taneja
MDL-35047 tool_xmldb: Added missing strings for xmldb
http://git.moodle.org/gw?p=moodle.git;a=commit;h=e71696e01255c5eb5b1b158ebbaf18e53b054e9e
http://github.com/moodle/moodle/commit/e71696e01255c5eb5b1b158ebbaf18e53b054e9e
+ 2.4 en [duplicateindexname,tool_xmldb]
+ 2.4 en [indexnameempty,tool_xmldb]
+ 2.4 en [incorrectindexname,tool_xmldb]