If a method or function refers to a type from an unbound package,
ignore it instead of reporting an error.
Change-Id: I689da63c1a0d1a3aa09220311d871c1f6f66208f
Reviewed-on: https://go-review.googlesource.com/20985
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
