Inlining isn't performed on generated init functions.  Removing the pair
function and initializing the structs directly saves another 16k on a
simple http.ListenAndServe() binary.

delta   name                                      old      new
-58     runtime.findfunctab                       10471    10413         -0.55%
-41     runtime.gcbss                             910      869           -4.51%
41      runtime.gcdata                            612      653            6.70%
-408    runtime.pclntab                           1036311  1035903       -0.04%
-11711  vendor/golang_org/x/net/http2/hpack.init  12283    572          -95.34%

Updates golang/go#6853

Change-Id: Ibccc796fe7403674cf4b4561acf9551d76ff11e8
Reviewed-on: https://go-review.googlesource.com/43190
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>