IR: Alloca clones should remember inalloca state

Pretty straightforward, we weren't propagating whether or not an
AllocaInst had 'inalloca' marked on it when it came time to clone it.

The inliner exposed this bug.  A reduced testcase is forthcoming.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207665 91177308-0d34-0410-b5e6-96231b3b80d8