patricia_trie: stop using 'siblings' member
patricia_trie: stop using 'siblings' member

It wasn't gaining us any performance (per testing),
which was its only reason for existence, and it uses up
memory space and code complication.  To be removed entirely in
next commit.

elidupree/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,Lasercake/Lasercake,elidupree/Lasercake,idupree/Lasercake,idupree/Lasercake,idupree/Lasercake,elidupree/Lasercake,elidupree/Lasercake,elidupree/Lasercake,idupree/Lasercake,Lasercake/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,idupree/Lasercake,idupree/Lasercake,Lasercake/Lasercake,idupree/Lasercake