* Break tests into individual cases so its easier to see what's going on.

* Add four new cases to handle the new optimizations for strlen, dealing
  with:
    strlen(x) != 0 -> *x != 0
    strlen(x) == 0 -> *x == 0
  for each of two cases: strlen(x) != 0 and strlen(x) == 0

llvm-svn: 21767