runtime: document FuncForPC behavior with inlining
runtime: document FuncForPC behavior with inlining

Change-Id: I1c02aa4f7131ae984fda66b32e8a993c0a40b8f4
Reviewed-on: https://go-review.googlesource.com/47690
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

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