Parse C++0x constexpr. Test case follows when this does something useful.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@86135 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Parse/DeclSpec.cpp b/lib/Parse/DeclSpec.cpp
index 3436900..0a4e036 100644
--- a/lib/Parse/DeclSpec.cpp
+++ b/lib/Parse/DeclSpec.cpp
@@ -334,6 +334,14 @@
   return false;
 }
 
+bool DeclSpec::SetConstexprSpec(SourceLocation Loc, const char *&PrevSpec,
+                                unsigned &DiagID) {
+  // 'constexpr constexpr' is ok.
+  Constexpr_specified = true;
+  ConstexprLoc = Loc;
+  return false;
+}
+
 void DeclSpec::setProtocolQualifiers(const ActionBase::DeclPtrTy *Protos,
                                      unsigned NP,
                                      SourceLocation *ProtoLocs,