[gtkdatabox] markers now use cairo

[Matt Flax <flatmax flatmax org>]

Hi there,

I have upgraded the markers code to use cairo to render instead of gdk_draw*
I compared the original markers.c example with the new markers.c example 
and they are virtually identical ... the main difference is that the 
boxes have nicer edges and the dashed lines are dashed in a slightly 
different way.

I grep'ed the code and find that there are still a few files which use 
gdk_draw routines rather then cairo ... these also need to be changed at 
some point.

Matt