compiler: improve recursive type detection

Detect recursive type definition like
"type T0 T1; type T1 T2; ...... type Tn T0".

Fixes golang/go#25320.

Change-Id: If2148b21c2857eec882309ea0cf4452209ebc6d5
Reviewed-on: https://go-review.googlesource.com/c/159837
Reviewed-by: Ian Lance Taylor <iant@golang.org>
1 file changed