[SYCL] Integrate sycl_special_class attribute (8ba9c79) to intel/llvm

The upstream patch triggered assertion on most of SYCL tests:
`AST/Decl.h:275: llvm::StringRef clang::NamedDecl::getName() const: Assertion Name.isIdentifier() && "Name is not a simple identifier"' failed.`

Fix includes the following changes:
* Check that name of function exists before trying to access it.
* Make sure that host accessor doesn't have sycl_special_class attribute
* Enable diagnostics for sycl_special_class attribute only for SYCL device compilation.

Author: Fznamznon

clang/lib/Sema/SemaDecl.cpp

@@ -9253,7 +9253,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
       }
       if ((Parent->isClass() || Parent->isStruct()) &&
           Parent->hasAttr<SYCLSpecialClassAttr>() &&
-          NewFD->getKind() == Decl::Kind::CXXMethod &&
+          NewFD->getKind() == Decl::Kind::CXXMethod && NewFD->getIdentifier() &&
           NewFD->getName() == "__init" && D.isFunctionDefinition()) {
         if (auto *Def = Parent->getDefinition())
           Def->setInitMethod(true);
@@ -16832,7 +16832,7 @@ void Sema::ActOnTagFinishDefinition(Scope *S, Decl *TagD,
 
   if (auto *RD = dyn_cast<CXXRecordDecl>(Tag)) {
     FieldCollector->FinishClass();
-    if (RD->hasAttr<SYCLSpecialClassAttr>()) {
+    if (RD->hasAttr<SYCLSpecialClassAttr>() && getLangOpts().SYCLIsDevice) {
       auto *Def = RD->getDefinition();
       assert(Def && "The record is expected to have a completed definition");
       unsigned NumInitMethods = 0;

sycl/include/CL/sycl/accessor.hpp

@@ -2200,8 +2200,8 @@ class __SYCL_SPECIAL_CLASS accessor<DataT, Dimensions, AccessMode,
 /// \ingroup sycl_api_acc
 template <typename DataT, int Dimensions, access::mode AccessMode,
           access::placeholder IsPlaceholder>
-class __SYCL_SPECIAL_CLASS accessor<DataT, Dimensions, AccessMode,
-                                    access::target::host_image, IsPlaceholder>
+class accessor<DataT, Dimensions, AccessMode, access::target::host_image,
+               IsPlaceholder>
     : public detail::image_accessor<DataT, Dimensions, AccessMode,
                                     access::target::host_image, IsPlaceholder> {
 public: