doc: complete remaining Go 1.9 documentation TODOs
doc: complete remaining Go 1.9 documentation TODOs

Updates #20587

Change-Id: Ie4846f90611390eebf037ffafaed5ddd273565e4
Reviewed-on: https://go-review.googlesource.com/47551
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

josharian/go,vsekhar/elastic-go,CAFxX/go,Cofyc/go,josharian/go,akutz/go,nawawi/go,cloudflare/go,Cofyc/go,cloudflare/go,CAFxX/go,akutz/go,vsekhar/elastic-go,golang/go,CAFxX/go,akutz/go,vsekhar/elastic-go,Cofyc/go,Cofyc/go,cloudflare/go,polyverse-security/go,josharian/go,cloudflare/go,codestation/go,golang/go,nawawi/go,josharian/go,CAFxX/go,vsekhar/elastic-go,codestation/go,akutz/go,nawawi/go,golang/go,codestation/go,josharian/go,polyverse-security/go,polyverse-security/go,vsekhar/elastic-go,polyverse-security/go,vsekhar/elastic-go,polyverse-security/go,codestation/go,akutz/go,josharian/go,nawawi/go,akutz/go,akutz/go,CAFxX/go,CAFxX/go,codestation/go,vsekhar/elastic-go,akutz/go,codestation/go,cloudflare/go,nawawi/go,codestation/go,golang/go,CAFxX/go,golang/go,nawawi/go,polyverse-security/go,golang/go,vsekhar/elastic-go,josharian/go,golang/go,cloudflare/go,nawawi/go,christopher-henderson/Go,Cofyc/go,josharian/go,cloudflare/go,codestation/go,Cofyc/go,Cofyc/go,Cofyc/go,polyverse-security/go,polyverse-security/go,cloudflare/go,CAFxX/go,nawawi/go,golang/go