upgrade irc-go to latest master

vendor/github.com/goshuirc/irc-go/ircmsg/message.go

@@ -52,10 +52,19 @@ type IrcMessage struct {
 	Prefix         string
 	Command        string
 	Params         []string
+	forceTrailing  bool
 	tags           map[string]string
 	clientOnlyTags map[string]string
 }
 
+// ForceTrailing ensures that when the message is serialized, the final parameter
+// will be encoded as a "trailing parameter" (preceded by a colon). This is
+// almost never necessary and should not be used except when having to interact
+// with broken implementations that don't correctly interpret IRC messages.
+func (msg *IrcMessage) ForceTrailing() {
+	msg.forceTrailing = true
+}
+
 // GetTag returns whether a tag is present, and if so, what its value is.
 func (msg *IrcMessage) GetTag(tagName string) (present bool, value string) {
 	if len(tagName) == 0 {
@@ -321,6 +330,10 @@ func (ircmsg *IrcMessage) LineBytesStrict(fromClient bool, truncateLen int) ([]b
 	return ircmsg.line(tagLimit, clientOnlyTagDataLimit, serverAddedTagDataLimit, truncateLen)
 }
 
+func paramRequiresTrailing(param string) bool {
+	return len(param) == 0 || strings.IndexByte(param, ' ') != -1 || param[0] == ':'
+}
+
 // line returns a sendable line created from an IrcMessage.
 func (ircmsg *IrcMessage) line(tagLimit, clientOnlyTagDataLimit, serverAddedTagDataLimit, truncateLen int) ([]byte, error) {
 	if len(ircmsg.Command) < 1 {
@@ -376,11 +389,12 @@ func (ircmsg *IrcMessage) line(tagLimit, clientOnlyTagDataLimit, serverAddedTagD
 
 	for i, param := range ircmsg.Params {
 		buf.WriteByte(' ')
-		if len(param) < 1 || strings.IndexByte(param, ' ') != -1 || param[0] == ':' {
-			if i != len(ircmsg.Params)-1 {
-				return nil, ErrorBadParam
-			}
+		requiresTrailing := paramRequiresTrailing(param)
+		lastParam := i == len(ircmsg.Params)-1
+		if (requiresTrailing || ircmsg.forceTrailing) && lastParam {
 			buf.WriteByte(':')
+		} else if requiresTrailing && !lastParam {
+			return nil, ErrorBadParam
 		}
 		buf.WriteString(param)
 	}