Hash maps now copy keys if keys are copyable.

test/unit/stdlib/collections/copy_map.c3

@@ -0,0 +1,30 @@
+module test;
+import std::io;
+import std::collections::map;
+
+fn void! copy_map() @test
+{
+	TrackingAllocator alloc;
+	alloc.init(mem::heap());
+	io::printfn("Heap mem: %d", alloc.allocated());
+    mem::@scoped(&alloc)
+	{
+		HashMap(<String, int>) x;
+		x.init();
+		DString y;
+		y.append("hello");
+		x.set(y.as_str(), 123);
+		y.append("bye");
+		x.set(y.as_str(), 333);
+		y.clear();
+		y.append("bye");
+		x.set(y.as_str(), 444);
+		assert(x.get("hello")! == 123);
+		assert(x.get("hellobye")! == 333);
+		assert(x.get("bye")! == 444);
+		assert(alloc.allocated() > 0);
+		x.free();
+		y.free();
+		assert(alloc.allocated() == 0);
+	};
+}