log: document that log messages end in newlines
log: document that log messages end in newlines

Fixes #16564.

Change-Id: Idd7b3c8f1d8415acd952d1efb6dc35ba4191805d
Reviewed-on: https://go-review.googlesource.com/31578
Run-TryBot: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Quentin Smith <d6b8e48afb2534b213e391cab43016505747a234@golang.org>

suncycheng/go,nawawi/go,christopher-henderson/Go,vsekhar/elastic-go,derekmarcotte/go,josharian/go,josharian/go,goodlang/good,josharian/go,polyverse-security/go,derekmarcotte/go,derekmarcotte/go,goodlang/good,Cofyc/go,akutz/go,vsekhar/elastic-go,polyverse-security/go,golang/go,linux-on-ibm-z/go,ImJasonH/go,goodlang/good,suncycheng/go,linux-on-ibm-z/go,nawawi/go,linux-on-ibm-z/go,polyverse-security/go,linux-on-ibm-z/go,goodlang/good,ImJasonH/go,polyverse-security/go,cloudflare/go,vsekhar/elastic-go,josharian/go,golang/go,ImJasonH/go,ImJasonH/go,nawawi/go,Cofyc/go,CAFxX/go,akutz/go,golang/go,akutz/go,CAFxX/go,goodlang/good,golang/go,cloudflare/go,cloudflare/go,akutz/go,golang/go,vsekhar/elastic-go,CAFxX/go,goodlang/good,akutz/go,linux-on-ibm-z/go,derekmarcotte/go,Cofyc/go,codestation/go,codestation/go,vsekhar/elastic-go,linux-on-ibm-z/go,CAFxX/go,codestation/go,josharian/go,akutz/go,cloudflare/go,codestation/go,derekmarcotte/go,codestation/go,nawawi/go,nawawi/go,suncycheng/go,Cofyc/go,CAFxX/go,CAFxX/go,golang/go,codestation/go,golang/go,nawawi/go,linux-on-ibm-z/go,cloudflare/go,derekmarcotte/go,CAFxX/go,ImJasonH/go,goodlang/good,goodlang/good,vsekhar/elastic-go,josharian/go,Cofyc/go,akutz/go,Cofyc/go,josharian/go,polyverse-security/go,suncycheng/go,golang/go,cloudflare/go,derekmarcotte/go,suncycheng/go,nawawi/go,codestation/go,akutz/go,codestation/go,polyverse-security/go,Cofyc/go,suncycheng/go,cloudflare/go,nawawi/go,CAFxX/go,Cofyc/go,ImJasonH/go,ImJasonH/go,polyverse-security/go,josharian/go,cloudflare/go,linux-on-ibm-z/go,vsekhar/elastic-go,vsekhar/elastic-go,suncycheng/go,derekmarcotte/go,suncycheng/go,polyverse-security/go,ImJasonH/go