Add unit test for name clashes with common "error" keyword

tests/unit/src/unit/issues/Issue5234.hx

@@ -0,0 +1,15 @@
+package unit.issues;
+
+class Issue5234 extends Test {
+	function test() {
+		var f = function(error){
+			throw error;
+		}
+		try{
+			f('test');
+			t(false);
+		} catch(e:Dynamic){
+			t(true);
+		}
+	}
+}