mm-qp-or-base64

[Michael.Cook@cisco.com]

pdf files often seem to look like plain text files because they tend
to contain a lot of "text" characters, especially at the beginning
of the file.  but pdf files also usually contain a lot of "binary"
characters.  in other words, mm-qp-or-base64 tends to return
'quoted-printable for pdf files, but it should probably return
'base64.  should we make mm-qp-or-base64 smarter?  maybe use
something like

 (goto-char (point-min))
 (if (looking-at "%PDF-")
    'base64
   ...)

suitably generalized, of course.  maybe with:

 (defvar mm-content-transfer-encoding-smart-defaults
   '(("\\`%PDF-" base64))
   "Alist of regexps to match against the beginning of a buffer
to determine which encoding to use.  If none of these regexps
matches, then a heuristic is applied to choose between
quoted-printable and base64.")

or maybe this idea could be folded into
mm-content-transfer-encoding-defaults somehow.

m.