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

This brings in:

aca852e Use x86_64_*_operand in LEA splitters

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3598
TEST= toolchain trybots
R=sehr@chromium.org

Review URL: https://codereview.chromium.org/21369003

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@11886 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