Merge of r51073-51074 from use-diet branch.

Do not rely on std::swap<Use>, provide a (faster) member function instead.
This change is primarily necessitated by MSVC++'s incompatibility with
declaring std::swap<Use> to be a friend of Use.

Also contains some minor tweaks to Use inline functions,
to undo pointless changes that sneaked in with the last merge.

llvm-svn: 51078
diff --git a/llvm/lib/VMCore/Instructions.cpp b/llvm/lib/VMCore/Instructions.cpp
index cea496d..ff56560 100644
--- a/llvm/lib/VMCore/Instructions.cpp
+++ b/llvm/lib/VMCore/Instructions.cpp
@@ -1563,7 +1563,7 @@
 bool BinaryOperator::swapOperands() {
   if (!isCommutative())
     return true; // Can't commute operands
-  std::swap(Op<0>(), Op<1>());
+  Op<0>().swap(Op<1>());
   return false;
 }