doc: flesh out some more Go 1.9 package notes
doc: flesh out some more Go 1.9 package notes

Change-Id: Ib6e2b858fcb15ea95fa8cfcba3bfac4e210605fe
Reviewed-on: https://go-review.googlesource.com/45610
Reviewed-by: Alberto Donizetti <90b16103a35511ced020676f3544f17117fb4c92@gmail.com>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

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