main.main and main.init were not being marked as reachable.

Fixes #17076

Change-Id: Ib3e29bd35ba6252962e6ba89173ca321ed6849b9
Reviewed-on: https://go-review.googlesource.com/28996Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>