ART: Fix things for valgrind

Wire up valgrind gtests. Add valgrind-test-art-host, currently
only depending on valgrind-test-art-host-gtest32.

Fix an Alloc setting to allow running valgrind.

Refactor the fault handler to manage (and correctly release) the
handlers.

Fix minor failure-case leaks exposed by tests.

Failing tests:

The optimizing compiler is leaking non-arena-ed structures
(e.g., assembler buffers), as code generators are not destroyed.
The solution has been moved to a follow-up CL.

Note: All 64b tests are failing as we cannot allocate a heap.

Change-Id: I7f854cfd098d9f68107ce492363e7dba9a82b9fa