Verify explicit instruction properties when they can be inferred.

It is now allowed to explicitly set hasSideEffects, mayStore, and
mayLoad on instructions with patterns.

Verify that the patterns are consistent with the explicit flags.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162569 91177308-0d34-0410-b5e6-96231b3b80d8