PNaCl: Add script for updating the Git revisions in pnacl/COMPONENT_REVISIONS
PNaCl: Add script for updating the Git revisions in pnacl/COMPONENT_REVISIONS

This is based on the llvm_deps_bump.py script from my nacl-dev-tools
Git repo that I and others have been using for a while.

BUG=none
TEST=run script (with "--list" and "-c gcc" etc.)

Review URL: https://codereview.chromium.org/46573005

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12346 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client