two changes:

- exported structs now get protected with #ifdef/#define blocks (allows including multiple ispc-generated header fiels into the same c source
- when creating offload stubs, encountering a 'export' function for which we cannot produce a stub will only trigger a warning, not an error.

type.h

@@ -381,6 +381,9 @@ public:
     std::string Mangle() const;
     std::string GetCDeclaration(const std::string &name) const;
 
+    /** Returns the name of the enum type.  (e.g. struct Foo -> "Foo".) */
+    const std::string &GetEnumName() const { return name; }
+
     llvm::Type *LLVMType(llvm::LLVMContext *ctx) const;
     llvm::DIType GetDIType(llvm::DIDescriptor scope) const;