[DVIPDFMx] dvipdfmx and pdf1.4

[Karl Berry]

    1. (XeTeX+xdvipdfmx) One way is to implement a new primitive \pdfminorversion
        that sends an option "-V 5" to xdvipdfmx. Another way is to do nothing and just
        use the new special command.
    2. (LaTeX+dvipdfmx) There is only one way using the new special command.

I'm guessing that Jonathan will prefer the "do nothing" alternative :),
so that the new special is used in just the same way for x and non-x
dvipdfmx.

    I will implement the new special as soon as possible.

Thanks much.  As previously discussed, I have hopes to start compiling
for TL 2010 soon.  (Reminds me ... Jonathan, are any XeTeX changes to
push into the TL repo?)

I have one other thought: inserting a special is vastly different than
setting a primitive register, since it affects the output stream.
Probably it should be done at the first shipout, and not anytime
earlier.  So, Manuel, I suppose that means involving atbegshi after
all.  We can discuss ...

Thanks,
k