unique_ptr-ify ownership of ASTConsumers

(after fixing a bug in MultiplexConsumer I noticed the ownership of the
nested consumers was implemented with raw pointers - so this fixes
that... and follows the source back to its origin pushing unique_ptr
ownership up through there too)
unique_ptr-ify ownership of ASTConsumers
Revert Thumb-2 conversion of some ARM builtins.

The udivmodsi4/modsi3/umodsi3 code computes jump targets based on ARM encodings
(if CLZ is present and IDIV is not present).

Reverts parts of r211032 and r211035.