Fix Id Literals so that they are keyed off an Id search. This allows us to add operator overloading on the parse side.

unittests/operator_overload.chai

@@ -0,0 +1,8 @@
+def Bob::`+`(y) { this.x + y.x }
+def Bob::Bob() { }
+attr Bob::x
+var b = Bob()
+var c = Bob()
+b.x = 4
+c.x = 5
+print(b+c)

unittests/operator_overload.txt

@@ -0,0 +1 @@
+9