More allocation code optimizations.

- Inline Class::AllocObject() and Array::Alloc().
- Inline some short Mutex functions and add LIKELY/UNLIKELY to some
  Mutex functions.
- This change improves the Ritz MemAllocTest by ~6% on Nexus 4 and
  ~10% on host.

Bug: 9986565
Change-Id: I1606c74ddb21676cbc1de1a40e9b076fc23eaea4
Merge "More allocation code optimizations." into kk44