Better error message for </tag>

[philshafer]

SLAX doesn't use close tags, but users sometimes mistakenly do. A better error message is needed:

"data { ... }

Gives:

/Users/phil/zap/ddos-under-attack-juniper.txt:23: unexpected input: '{'; expected valid XPath expression
/Users/phil/zap/ddos-under-attack-juniper.txt:34: unexpected input: '}'; expected valid top-level statement