- zint_symbol->fgcolour & bgcolour buffer lengths extended 10

-> 16 to allow for "C,M,Y,K" comma-separated decimal percentage
  strings
- API/CLI/GUI: allow foreground/background colours to be specified
  as comma-separated decimal "C,M,Y,K" strings where "C", "M" etc.
  are percentages (0-100) (ticket #281, 3rd point)
- output.c: new funcs `out_colour_get_rgb()` & `out_colour_get_cmyk()`
  and use in bmp/emf/gif etc.
- PCX: add alpha support
- GUI: fix fg/gbcolor icon background not being reset on zap
- GUI: Rearrange some Appearance tab inputs (Border Type <-> Width,
  Show Text <-> Font, Text/Font <-> Printing Scale/Size) to flow
  more naturally (hopefully)
- GUI: save button "Save As..." -> "Save..." and add icon
- CLI: add --bgcolor/colour & --fgcolor/colour synonyms

backend/tests/data/eps/code39_fg_bg.eps

@@ -1,5 +1,5 @@
 %!PS-Adobe-3.0 EPSF-3.0
-%%Creator: Zint 2.10.0.9
+%%Creator: Zint 2.12.0.9
 %%Title: Zint Generated Symbol
 %%Pages: 0
 %%BoundingBox: 0 0 128 119
@@ -8,10 +8,10 @@
 /TR { newpath 4 1 roll exch moveto 1 index 0 rlineto 0 exch rlineto neg 0 rlineto closepath fill } bind def
 /TE { pop pop } bind def
 newpath
-0.98 0.59 0.19 setrgbcolor
+0.99 0.59 0.19 setrgbcolor
 118.90 0.00 TB 0.00 128.00 TR
 TE
-0.08 0.48 0.81 setrgbcolor
+0.08 0.48 0.82 setrgbcolor
 100.00 18.90 TB 0.00 2.00 TR
 TE
 100.00 18.90 TB 6.00 2.00 TR