Slightly alter tag hierarchy so that Empty doesn't inherit from Start.
Slightly alter tag hierarchy so that Empty doesn't inherit from Start.

git-svn-id: 07e90cf55c51d05f6e47e58d22f17c514a1aa358@33 48356398-32a2-884e-a903-53898d9a118a

r-kovalenko/htmlpurifier,stefanotorresi/htmlpurifier,Janson-Leung/htmlpurifier,stefanotorresi/htmlpurifier,r-kovalenko/htmlpurifier,ezyang/htmlpurifier,bartbutler/htmlpurifier,Masterjoa/HTMLPurifier-standalone,Masterjoa/HTMLPurifier-standalone,bfroehle/htmlpurifier,stefanotorresi/htmlpurifier,bfroehle/htmlpurifier,Janson-Leung/htmlpurifier,Janson-Leung/htmlpurifier,r-kovalenko/htmlpurifier,stefanotorresi/htmlpurifier,ezyang/htmlpurifier,ezyang/htmlpurifier,bartbutler/htmlpurifier,bartbutler/htmlpurifier,bfroehle/htmlpurifier,ezyang/htmlpurifier,r-kovalenko/htmlpurifier,Janson-Leung/htmlpurifier,bartbutler/htmlpurifier