Explicitly request unsigned enum types when desired

This fixes repeated -Wmicrosoft warnings when self-hosting clang on
Windows, and gets us real unsigned enum types with MSVC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192227 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp
index f094c4c..3fa5243 100644
--- a/lib/CodeGen/RegAllocGreedy.cpp
+++ b/lib/CodeGen/RegAllocGreedy.cpp
@@ -222,7 +222,7 @@
   /// class.
   SmallVector<GlobalSplitCandidate, 32> GlobalCand;
 
-  enum { NoCand = ~0u };
+  enum LLVM_ENUM_INT_TYPE(unsigned) { NoCand = ~0u };
 
   /// Candidate map. Each edge bundle is assigned to a GlobalCand entry, or to
   /// NoCand which indicates the stack interval.