goprotobuf: update tags for weekly.

R=dsymonds
CC=golang-dev
http://codereview.appspot.com/5307067

.hgtags

@@ -15,3 +15,4 @@ da17c98c73d8801baa1d2e493c9ac0844470ef0a release.r59
 f0f9983b6de6764a416f90d31440f01b54233228 go.r60
 5a487ccac6f7fd6cba5deee5d5d0908c7f1d6a53 go.weekly.2011-09-07
 bc76a153ffde5de8535b7c2791102ddd0b93f187 go.weekly.2011-09-21
+a13c0e6343c49dc738c218ea43cab675865136dc go.weekly.2011-10-26