Add deprecation of neverHasSideEffects to documentation comments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175175 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64: switch from neverHasSideEffects to hasSideEffects.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175176 91177308-0d34-0410-b5e6-96231b3b80d8