add test for getting position of a static extension method (closes #1968)

tests/misc/projects/Issue1968/Main.hx

@@ -0,0 +1,11 @@
+using Main.A;
+
+class A {
+    public static function f(v:String, b:Int):String return v;
+}
+
+class Main {
+    static function main() {
+        "a".f
+    }
+}

tests/misc/projects/Issue1968/compile.hxml

@@ -0,0 +1 @@
+--display Main.hx@147@position

tests/misc/projects/Issue1968/compile.hxml.stderr

@@ -0,0 +1,3 @@
+<list>
+<pos>$$normPath(::cwd::/Main.hx):4: characters 18-61</pos>
+</list>