Fix three bugs:

Fix three bugs:

1) evaluate [v]fcmp true/false with undefs to true or false instead
   of undef.
2) fix vector comparisons with undef to return a vector result instead
   of i1
3) fix vector comparisons with evaluatable results to return vector
   true/false instead of i1 true/false (PR2529)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53220 91177308-0d34-0410-b5e6-96231b3b80d8