runtime: use staticbytes in intstring for small v
runtime: use staticbytes in intstring for small v

Triggers 21 times during make.bash.

Change-Id: I7efb34200439256151304bb66cd309913f7c9c9e
Reviewed-on: https://go-review.googlesource.com/110557
Run-TryBot: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Martin Möhrmann <9c82b83f348009b39856043bb9ed3ef41e171aeb@google.com>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/go,cloudflare/go,cloudflare/go,nawawi/go,golang/go,cloudflare/go,akutz/go,akutz/go,golang/go,josharian/go,josharian/go,nawawi/go,CAFxX/go,josharian/go,golang/go,golang/go,CAFxX/go,akutz/go,cloudflare/go,akutz/go,josharian/go,josharian/go,cloudflare/go,josharian/go,golang/go,CAFxX/go,CAFxX/go,josharian/go,nawawi/go,CAFxX/go,CAFxX/go,nawawi/go,CAFxX/go,cloudflare/go,josharian/go,akutz/go,nawawi/go,golang/go,golang/go,akutz/go,cloudflare/go,nawawi/go,akutz/go,cloudflare/go,nawawi/go,CAFxX/go,akutz/go,nawawi/go