Handle godef "no object" error

Improve successful output parsing to detect newest godef giving
output: no object

Closes: #351 [via git-merge-pr]

Author: wuurrd

go-mode.el

@@ -2336,6 +2336,7 @@ description at POINT."
 (defun godef--successful-p (output)
   (not (or (string= "-" output)
            (string= "godef: no identifier found" output)
+           (string= "godef: no object" output)
            (go--string-prefix-p "godef: no declaration found for " output)
            (go--string-prefix-p "error finding import path for " output))))