Add a bunch of TMP support.

I'm still on the fence about going full `constexpr` functions
for meta-code.  Overall, I think there's potential here.  I'm
not aiming to replicate what `boost::mpl` or `boost::hana` do
though.  This is more of an internal support mechanism for
Alepha code.  As-needed I'll implement things.

Meta/functional.h

@@ -0,0 +1,42 @@
+static_assert( __cplusplus > 201700, "C++17 Required" );
+
+#pragma once
+
+// Analogue to `#include <functional>`
+
+#include <Alepha/Alepha.h>
+
+namespace Alepha::Hydrogen::Meta
+{
+	inline namespace exports { inline namespace functional {} }
+
+	namespace detail::functional
+	{
+		inline namespace exports
+		{
+			template< template< typename, typename > class Function, typename First >
+			struct bind1st
+			{
+				using type= bind1st;
+				template< typename Arg >
+				struct call : Function< First, Arg >::type {};
+			};
+
+			template< template< typename, typename > class Function, typename Second >
+			struct bind2nd
+			{
+				using type= bind2nd;
+				template< typename Arg >
+				struct call : Function< Arg, second >::type {};
+			};
+
+			template< typename Function, typename ... Args >
+			struct call : Function::template call< Args... > {};
+		}
+	}
+
+	namespace exports::functional
+	{
+		using namespace detail::functional::exports;
+	}
+}