Work around exception on spammy mail...

Don't include the obsolete unstructured regex in abs.unstrctured,
and use the abnf.unstructured for parsing headers.

This fixes an issue seen running the IMAP server on gratuitously
spammy messages.

exec/load/mime.js

@@ -354,7 +354,8 @@ abnf.obs_phrase="(?:"+abnf.word+"(?:"+abnf.word+"|\\.|"+abnf.CFWS+")*)";
 abnf.phrase=abnf.obs_phrase;
 
 // 3.2.5 Miscellaneous Tokens
-abnf.unstructured=abnf.obs_unstruct;
+//abnf.unstructured=abnf.obs_unstruct;
+abnf.unstructured="(?:(?:"+abnf.FWS+"?"+abnf.VCHAR+")*"+abnf.WSP+"*)";
 
 // 3.3 Date and Time Specification
 abnf.day_name="(?:Mon|Tue|Wed|Thu|Fri|Sat|Sun)";
@@ -603,7 +604,7 @@ function parse_header(str)
 	var m;
 	var re;
 
-	re=new RegExp("^("+abnf.field_name+")"+abnf.WSP+"*:"+rfc5322abnf.unstructured+""+abnf.CRLF,"i");
+	re=new RegExp("^("+abnf.field_name+")"+abnf.WSP+"*:"+abnf.unstructured+""+abnf.CRLF,"i");
 	m=re.exec(str);
 	if(m==null)
 		return(undefined);