Add nice error messages for unsupported && and ||

As explained in issue #1273, `operator&&` and `operator||` should give
a proper compile time error on use instead of the compiler complaining
about them not being defined. This commit adds an `always_false` type in
`catch_meta.hpp` used for implementing a nice `static_assert` for both
of the abovementioned operators.

Closes #1273

include/internal/catch_meta.hpp

@@ -9,6 +9,8 @@
 #ifndef TWOBLUECUBES_CATCH_META_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_META_HPP_INCLUDED
 
+#include <type_traits>
+
 template< typename... >
 struct TypeList{};
 
@@ -73,4 +75,7 @@ struct combine
     };
 };
 
+template<typename T>
+struct always_false : std::false_type {};
+
 #endif // TWOBLUECUBES_CATCH_META_HPP_INCLUDED