.hgtags: add tag for release.r58.1.

TBR=r
CC=golang-dev
http://codereview.appspot.com/4711042

.hgtags

@@ -9,4 +9,5 @@ f3ef978cda6fabc10f6039aeed960340547c6d5a release.r56
 fa1080cfc0a4d0fa24844bc50124aed892365059 release.r57.1
 fa1080cfc0a4d0fa24844bc50124aed892365059 release.r57.2
 cfe37a63cede6cd072434965e6ea426b90bcb223 release.r58
+cfe37a63cede6cd072434965e6ea426b90bcb223 release.r58.1
 cfe37a63cede6cd072434965e6ea426b90bcb223 release