-registering same system multiple times only replace pointer for callback

-added export attributes (required by windows to make DLL library, not work at now due to DMD bugs)
-interface D files to import

import/ecs/traits.di

@@ -0,0 +1,20 @@
+// D import file generated from 'source\ecs\traits.d'
+module ecs.traits;
+import std.traits;
+bool isForeachDelegateWithI(DG)()
+{
+	return is(DG == delegate) && is(ReturnType!DG == int) && (Parameters!DG.length == 2) && isIntegral!(Parameters!DG[0]);
+}
+bool isForeachDelegateWithoutI(DG)()
+{
+	return is(DG == delegate) && is(ReturnType!DG == int) && (Parameters!DG.length == 1);
+}
+bool isForeachDelegateWithTypes(DG, Types...)()
+{
+	return is(DG == delegate) && is(ReturnType!DG == int) && is(Parameters!DG == Types);
+}
+auto assumeNoGC(T)(T t) if (isFunctionPointer!T || isDelegate!T)
+{
+	enum attrs = functionAttributes!T | FunctionAttribute.nogc;
+	return cast(SetFunctionAttributes!(T, functionLinkage!T, attrs))t;
+}