abi2: bugfix. not matching events based on number of indexed fields

I noticed that certain abi events were not being saved to my table and
upon further inspection I realized that when I had setup my integration
I only selected 1 out of 3 of the indexed fields on the event.

When an integration is testing a log to see if it should index it, it
uses two methods:

1. topics[0] byte comparison
2. the number of non-empty remaining topics matches number of indexed
   inputs in the abi

In my case, the 2nd method was failing because of a bug. The code was
reporting the number of indexed inputs based upon the selected inputs.
Instead, we should simply look at all the top level inputs to see if
Indexed=true.

abi2/abi2.go

@@ -537,7 +537,7 @@ func (e Event) Selected() []Input {
 
 func (e Event) numIndexed() int {
 	var res int
-	for _, inp := range e.Selected() {
+	for _, inp := range e.Inputs {
 		if inp.Indexed {
 			res++
 		}

abi2/abi2_test.go

@@ -299,3 +299,15 @@ func TestSelected(t *testing.T) {
 	}
 	diff.Test(t, t.Errorf, want, event.Selected())
 }
+
+func TestNumIndexed(t *testing.T) {
+	event := Event{
+		Name: "",
+		Inputs: []Input{
+			Input{Indexed: true, Name: "a"},
+			Input{Indexed: true, Name: "b", Column: "b"},
+			Input{Indexed: true, Name: "c", Column: "c"},
+		},
+	}
+	diff.Test(t, t.Errorf, 3, event.numIndexed())
+}