Remove BitVector binops.

Remove BitVector binops.

These operators were crazy slow, calling malloc to return a temporary
result. At the same time, they look very innocent when used in code.

If you need temporary BitVectors to compute your thing, create them
explicitly, and use the inplace logical operators. This makes the high
cost explicit in the code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156767 91177308-0d34-0410-b5e6-96231b3b80d8