Previously we'd not clang-formatted the c++ bytecode files because:
A) It's a massive difference in format
B) I wasn't sure, at the time, which code was "ours"
Reformatting now that the LLVM source is all removed and before it gets
updated to support modern LLVM versions.
Internal version is an LLVM 2.8 with 2 patches backported from LLVM 2.9 to fix a
crash on AVX chips.
So drop support for building with external LLVM 2.8, and add support for
building with external LLVM 2.9 instead.
Caveat:
stack smashing protection is broken on LLVM 2.9 so it is disabled
Example on Debian:
apt-get install llvm-2.9-dev
./configure --enable-llvm --with-system-llvm=/usr/bin/llvm-config-2.9
