Fix missing typename/template error with Clang

Author: ecorm

cppwamp/include/cppwamp/internal/options.ipp

@@ -58,12 +58,7 @@ Variant Options<D>::optionByKey(const String& key) const
 //------------------------------------------------------------------------------
 template <typename D>
 template <typename T>
-#ifdef CPPWAMP_FOR_DOXYGEN
-ValueTypeOf<T>
-#else
-Options<D>::ValueTypeOf<T>
-#endif
-Options<D>::optionOr(
+ValueTypeOf<T> Options<D>::optionOr(
     const String& key, /**< The key to search under. */
     T&& fallback       /**< The fallback value to return if the key was
                             not found. */

cppwamp/include/cppwamp/options.hpp

@@ -8,6 +8,7 @@
 #ifndef CPPWAMP_OPTIONS_HPP
 #define CPPWAMP_OPTIONS_HPP
 
+#include "traits.hpp"
 #include "variant.hpp"
 #include "./internal/passkey.hpp"
 
@@ -26,10 +27,6 @@ template <typename TDerived>
 class Options
 {
 public:
-    /** Metafunction used to obtain the plain value type of a parameter
-        passed by universal reference. */
-    template <typename T> using ValueTypeOf = typename std::decay<T>::type;
-
     /** Adds an option. */
     TDerived& withOption(String key, Variant value);