As gfx_canvas_t now has excatly the same lifespan as image_desc_t, I've

made 'gfx_canvas_t canvas' a member of image_desc_t and dropped it as a
separate parameter in all function calls.

imgformat, interlaced and zoom are moved to gfx_canvas_t. I have dropped
my old fontlib-enum as imgformat contains that information. The
gfx_render_xxx switch is moved to rrd_gfx so rrd_graph is (almost) only
bothered with image formats in cmd line parsing.

gfx_close_path is added.

gfx_new_dashed_line is added with 2 new arguments: length of a dash and
length between dashes. gfx_new_line is still there for plain lines.
Having dash-length == 0 creates normal line.
rrd_graph.c is not updated for dashed lines. It's not decided how one
should specify which and how lines are dashed. An extension of the color
specification?

svg is updated for dashes and opacity, but libart code is not. I've
fixed indent in SVG, all lines had a space before func decl. etc.
Misc small fixes, e.g. sscanf of gfx_color_t, position of x-axis arrow.
--- Peter Speck <speck@ruc.dk>

git-svn-id: svn://svn.oetiker.ch/rrdtool/trunk/program@114 a5681a0c-68f1-0310-ab6d-d61299d08faa