strconv: unify error creation in ParseUint with ParseInt
strconv: unify error creation in ParseUint with ParseInt

Remove goto and use helper functions in ParseUint to create errors.

Change-Id: I1c4677ae1b9980db79065a9f8ca1f2c470249505
Reviewed-on: https://go-review.googlesource.com/55135
Run-TryBot: Martin Möhrmann <9c82b83f348009b39856043bb9ed3ef41e171aeb@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Joe Tsai <7277d7402195d5c2006c89f45718cf82bb3e527f@gmail.com>

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