Implement Haxe 5's Map.size

Author: SomeRanDev

std/cxx/_std/haxe/ds/IntMap.hx

@@ -77,4 +77,10 @@ class IntMap<T> implements haxe.Constraints.IMap<Int, T> {
 	public function clear(): Void {
 		m.clear();
 	}
+
+	#if haxe5
+	public function size(): Int {
+		m.size();
+	}
+	#end
 }

std/cxx/_std/haxe/ds/ObjectMap.hx

@@ -77,4 +77,10 @@ class ObjectMap<K:{}, V> implements haxe.Constraints.IMap<K, V> {
 	public function clear(): Void {
 		m.clear();
 	}
+
+	#if haxe5
+	public function size(): Int {
+		m.size();
+	}
+	#end
 }

std/cxx/_std/haxe/ds/StringMap.hx

@@ -74,7 +74,9 @@ class StringMap<T> implements haxe.Constraints.IMap<String, T> {
 		return result + "]";
 	}
 
-	public function clear(): Void {
-		m.clear();
+	#if haxe5
+	public function size(): Int {
+		m.size();
 	}
+	#end
 }