PNaCl: Update LLVM revision in pnacl/COMPONENT_REVISIONS
PNaCl: Update LLVM revision in pnacl/COMPONENT_REVISIONS

This pulls in the following LLVM change:

7afd189: (dschuff@chromium.org) Do not tailcall optimize vararg calls with 6 arguments

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4123
TEST= PNaCl toolchain trybots
TBR=jfb

Review URL: https://codereview.chromium.org/1041043007

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