#13 Crash from bad encoded-word decoding

[Anonymous]

RFC2047 specifies how MIME encoded-words in headers
should be detected and decoded. trn (as of 4.0-test76)
does not follow this specification, and gets confused
trying to detect such an encoded-word crossing a line
boundary, so causing a crash. Example article:

Subject: Not MIME (may crash trn4)
From: jsm28-=?us-ascii?Q?=46=6F=6F@srcf.ucam.org
(?= Joseph Myers)
Newsgroups: foo.bar
Date: Sun, 13 Feb 2000 21:32:02 GMT
Message-ID: <foo@bar.invalid>
Lines: 2

The From header should not be interpreted as including
an RFC 2047 encoded-word. trn4 is broken here.