Possible integration of xpost and LibreOffice

[luser- -droog]

I've been contacted by a few devs at LibreOffice to see
if xpost could be used to render/import EPS files.
And LibreOffice has the backend that I need for the graphics
part. So it'll be pretty cool if we can get it to work.

I've been looking at the code for their svg module, as xpost
should ideally interface in a similar manner. It appears to
use a C++ interface similar to that describe in
http://en.wikipedia.org/wiki/Dynamic_loading
but the function pointers are wrapped in a struct so they
can safely be exported via a void *ptr.


Xpost itself is finally running a real executive (read-in from
source), but the error mechanism still needs some work. And I
need to do a slow pass through each operator, checking that each
one is signaling all appropriate errors and respecting access
flags (and hopefully performing the correct operation!).

Then there's quite a bit of Level-2 stuff I need to start
considering (thus far having had quite plateful without it).
Filtered files, Resources, Binary Encoding, faking packedarrays.
(I've quite given up any hope of understanding how real packed
arrays work. My SO question
(http://stackoverflow.com/q/7346544/733077)
having gathered little insight.)