doc: use existence of parens to decide how to handle comments in GenDecls Also use correct #tags for godoc.org; they are different from golang.org's.
doc: use existence of parens to decide how to handle comments in GenDecls
Also use correct #tags for godoc.org; they are different from golang.org's.

R=r
https://golang.org/cl/7760046

tiago4orion/doc,robpike/doc