Put private class into an anonmyous namespace.

llvm-svn: 178420
diff --git a/llvm/lib/Support/MemoryBuffer.cpp b/llvm/lib/Support/MemoryBuffer.cpp
index 8042237..7c5ab96 100644
--- a/llvm/lib/Support/MemoryBuffer.cpp
+++ b/llvm/lib/Support/MemoryBuffer.cpp
@@ -72,10 +72,12 @@
   Memory[Data.size()] = 0; // Null terminate string.
 }
 
+namespace {
 struct NamedBufferAlloc {
   StringRef Name;
   NamedBufferAlloc(StringRef Name) : Name(Name) {}
 };
+}
 
 void *operator new(size_t N, const NamedBufferAlloc &Alloc) {
   char *Mem = static_cast<char *>(operator new(N + Alloc.Name.size() + 1));