Revert "LLVMContext: Store APInt/APFloat directly into the ConstantInt/FP DenseMaps."

Somehow made DenseMap probe on forever on 32 bit machines.
This reverts commit r223478.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223546 91177308-0d34-0410-b5e6-96231b3b80d8