IR: Take uint64_t in DIBuilder::createExpression()

`DIExpression` deals with `uint64_t`, so it doesn't make sense that
`createExpression()` is created from `int64_t`.  Switch to `uint64_t` to
unify them.

I've temporarily left in the `int64_t` version, which forwards to the
`uint64_t` version.  I'll delete it once I've updated the callers.

llvm-svn: 228619
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index c2dfaf5..b8c0a7e 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1123,7 +1123,7 @@
     // "deref" operation to a list of address elements, as new llvm.dbg.declare
     // will take a value storing address of the memory for variable, not
     // alloca itself.
-    SmallVector<int64_t, 4> NewDIExpr;
+    SmallVector<uint64_t, 4> NewDIExpr;
     NewDIExpr.push_back(dwarf::DW_OP_deref);
     if (DIExpr)
       for (unsigned i = 0, n = DIExpr.getNumElements(); i < n; ++i)