-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/string_intern.di

@@ -0,0 +1,31 @@
+// D import file generated from 'source\ecs\string_intern.d'
+module ecs.string_intern;
+import ecs.hash_map;
+import ecs.traits : isForeachDelegateWithI;
+import std.experimental.allocator;
+import std.experimental.allocator.mallocator;
+import std.traits : Parameters;
+private static __gshared HashMap!(const(char)[], StringIntern) gStringInterns;
+struct StringIntern
+{
+	private const(char)* strPtr;
+	this(const(char)[] fromStr)
+	{
+		opAssign(fromStr);
+	}
+	void reset();
+	size_t length();
+	const(char)[] str();
+	const(char)[] cstr();
+	bool opEquals()(auto ref const StringIntern s)
+	{
+		return strPtr == s.strPtr;
+	}
+	bool opEquals()(auto ref const(char[]) s)
+	{
+		return str() == s;
+	}
+	void opAssign(const(char)[] fromStr);
+	const(char)[] opSlice();
+	private const(char)[] allocStr(const(char)[] fromStr);
+}