Bump version to 2.12.0-dev

[skip ci]

Signed-off-by: Neil Twigg <neil@nats.io>

Author: neilalexander

server/const.go

@@ -58,7 +58,7 @@ func init() {
 
 const (
 	// VERSION is the current version for the server.
-	VERSION = "2.11.3"
+	VERSION = "2.12.0-dev"
 
 	// PROTO is the currently supported protocol.
 	// 0 was the original