1. Fix bug test/Regression/Other/2002-03-20-LevelRaiseBadCodegen.ll

1. Fix bug test/Regression/Other/2002-03-20-LevelRaiseBadCodegen.ll
2. Allow negative scales in ConvertableToGEP, so that this loop from
   alloc_tree in the Olden health benchmark is correctly raised:

       for (i = 3; i >= 0; i--)
         fval[i] = alloc_tree(level - 1, label*4 + i + 1, new);

   Stepping through the array backwards caused a negative scale.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1922 91177308-0d34-0410-b5e6-96231b3b80d8