This is based on a list that Austin Clements provided in mid-2016. It is
mostly untouched, except for the fact that the wbufptr funcs were
removed from the runtime thus removed from the lits here too.

Add a section for these GC funcs, since there are quite a lot of them
and the runtime has tons of funcs that we want to inline. As before,
sort this section too.

Also place some of these funcs out of the GC section, as they are not
directly related to the GC.

Updates #21851.

Change-Id: I35eb777a4c50b5f655618920dc2bc568c7c30ff5
Reviewed-on: https://go-review.googlesource.com/65654
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>