Reverting back to the previous revision.

We want to check for length 5 because we might get the "llvm." string as the
name.  That string is in the LLVM namespace and should be checked as such.
We also don't have to worry about garbage data because (I believe) the string
class will return a valid value.  So, the switch statement will work and we
don't have to worry about the code wandering into segfault land.

llvm-svn: 8419