1. Make sure all delete operators of arrays use the array form of delete.

1. Make sure all delete operators of arrays use the array form of delete.
2. Rewrite operator=(const APInt& RHS) to allow the RHS to be a different
   bit width than the LHS. This makes it possible to use APInt as the key
   of a DenseMap, as needed for the IntConstants map in Constants.cpp
3. Fix operator=(uint64_t) to clear unused bits in case the client assigns
   a value that has more bits than the APInt allows.
4. Assert that bit widths are equal in operator==
5. Revise getHashValue() to put the bit width in the low order six bits.
   This should help to make i1 0, i2 0, ... i64 0 all distinct in the
   IntConstants DenseMap.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34646 91177308-0d34-0410-b5e6-96231b3b80d8