More reliable stack unwinding in Valgrind interceptors.
More reliable stack unwinding in Valgrind interceptors.

The previous solution depended on gcc not generating a frame pointer for the
interceptor functions. This one requires up to 2 extra registers, but should
work in any situation.
Review URL: http://codereview.chromium.org/3135052

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@3123 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client