Update gcc revision in tools/REVISIONS
Update gcc revision in tools/REVISIONS

This brings in:

46c2b9f Use long long builtins of zero counting for x86-64.

R=halyavin@google.com

Review URL: https://codereview.chromium.org/22280008

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@11968 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

Lind-Project/native_client,Lind-Project/native_client,Lind-Project/native_client,Lind-Project/native_client,Lind-Project/native_client,Lind-Project/native_client