Add small thread-local cache for use by the interpreter.

Small (one page) cache which can be used on the hottest paths
in the interpreter and which does not require synchronisation.
This CL adds the code but it does not use it for anything yet.

Test: test-art-host-gtest
Change-Id: I41d4e7a86a0f62f7a4efc165b8934232b4e766c7