ticket:9721: Change version number to 51.1 and update timebombs

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@33347 251d0590-4201-4cf1-90de-194747b24ca1
ticket:9988: remove poor mans RTTI from new class hierarchy, remove undocumented UNDEFINED_NUMERIC_CODE, fix destructor definition, not intended for public subclassing

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@33348 251d0590-4201-4cf1-90de-194747b24ca1