LLVM 2.8 is available

i haven't had time for benchmarks (and i don't actually know what would exercise various kernel subsystems/paths well enough, kernel compilation isn't exactly it ;) but based on the generated code and overall code size, clang generates about 3% fatter code than gcc (at least with -Os, i didn't try -O2). as for compile time, i only tested llvm 2.7 last spring and the times for compiling the same kernel/.config were something like this: gcc 4.4.x: 20 mins, llvm-gcc: 18 mins, clang: 16 mins.