Tune compression:

bzip2: block size 9 -> 5, reduces memory by 400Kbytes, doesn't affect speed
       or compression ratio on all but the largest bytecode files (>1MB)
zip:   level 9 -> 6, this speeds up compression time by ~30% but only
       degrades the compressed size by a few bytes per megabyte. Those few
       bytes aren't worth the effort.

llvm-svn: 17647