(nndoc-type-alist, nndoc-lanl-gov-announce-type-p)

(nndoc-type-alist, nndoc-lanl-gov-announce-type-p)
(nndoc-transform-lanl-gov-announce, nndoc-generate-lanl-gov-head):
Recognize math postings properly.  Extract Date and email address
correctly.  Create Date and From header for revised versions.  Get
rid of spurious \\ lines.  Detect end of message correctly.
Correctly rephrase the URL.