SyslogToMapTransformer doesn't split TAG and MESSAGE fields correctly

Regular expression used in SyslogToMapTransformer to split text into Map fields is not splitting TAG and MESSAGE fields correctly.

According to RFC 3164, chapter "4.1.3 MSG Part of a syslog Packet":

the first character of the CONTENT field that signifies the
conclusion of the TAG field has been seen to be the left square
bracket character ("["), a colon character (":"), or a space
character. This is explained in more detail in Section 5.3.

Pattern should finish TAG field on any non-alphanumeric character but right now it only looks for colon.