go/packages/packagestest: allow expectations to have *regexp.Regexp and interface{} parameters
go/packages/packagestest: allow expectations to have *regexp.Regexp and interface{} parameters

Change-Id: I86312ae2f30ba04290e9b7a001e0284439f4bfe6
Reviewed-on: https://go-review.googlesource.com/c/151346
Run-TryBot: Ian Cottrell <52376736e5e84615ec49f9c1843b8acc178b1d8d@google.com>
Reviewed-by: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools