A node spans multiple lines if the line difference
between start and end point is > 0 (rather than > 1).
Fixes some odd cases introduced by CL 5706055;
pointed out by dsymonds.

Added corresponding test case. The other change
in the .golden file reverts to the status before
the CL mentioned above and is correct.

gofmt -w src misc changes godoc.go back to where
it was before the CL mentioned above.

Fixes #3304.

R=dsymonds, rsc
CC=golang-dev
https://golang.org/cl/5820044