internal/gopathwalk/walk: add missing function descriptions and renaming
internal/gopathwalk/walk: add missing function descriptions and renaming

Missing function descriptions are added. init is renamed setIgnoredDirs.

Change-Id: I56b5a7c3e4fcc27991b33aef16d506948ce4b36b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/208358
Reviewed-by: Ian Cottrell <52376736e5e84615ec49f9c1843b8acc178b1d8d@google.com>

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