Add support for a new type of frame data record seen in a k18 file, and

Add support for a new type of frame data record seen in a k18 file, and
handle that file not ending with a 2-byte 0xffff end-of-file record.

This fixes bug 9455, although it doesn't add support for reading an
"index" file for a capture that's in multiple .rf5 files, which is a
separate issue noted in that bug.

It also doesn't attempt to figure out what the data in the new record
type following the data that appears to be the same as that in the other
data record format but preceding the actual packet data is.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@53452 f5534014-38df-0310-8fa8-9805f1628bb7