output: Add initial support for PSPP output via Cairo.

output: Add initial support for PSPP output via Cairo.

This commit adds some support for PSPP output using Cairo.  For now, that
means that you can produce PDF, PostScript, and SVG output to files if you
have Cairo and Pango available.

The output isn't perfect.  Descenders in text sometimes stick out beyond
table cell boundaries.  Charts aren't supported.  There is no
documentation update.  And I've tested it on a grand total of 1 (one!)
input file.  But I'm pushing out now for anyone who's interested.