[OpenCL] Allow addr space spelling without __ prefix in C++.

For backwards compatibility we allow alternative spelling of address
spaces - 'private', 'local', 'global', 'constant', 'generic'.

In order to accept 'private' correctly, parsing has been changed to
understand different use cases - access specifier vs address space.

Fixes PR40707 and PR41011!

Differential Revision: https://reviews.llvm.org/D59603

llvm-svn: 356888
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 895aa02..fe9fa10 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -3047,9 +3047,14 @@
     DiagnoseUnexpectedNamespace(cast<NamedDecl>(TagDecl));
     return nullptr;
 
+  case tok::kw_private:
+    // FIXME: We don't accept GNU attributes on access specifiers in OpenCL mode
+    // yet.
+    if (getLangOpts().OpenCL && !NextToken().is(tok::colon))
+      return ParseCXXClassMemberDeclaration(AS, AccessAttrs);
+    LLVM_FALLTHROUGH;
   case tok::kw_public:
-  case tok::kw_protected:
-  case tok::kw_private: {
+  case tok::kw_protected: {
     AccessSpecifier NewAS = getAccessSpecifierIfPresent();
     assert(NewAS != AS_none);
     // Current token is a C++ access specifier.