[cogl-pango-render] Fix returning to default color after a color attribute
[cogl-pango-render] Fix returning to default color after a color attribute

Since the Cogl material branch merge when changing the color of a part
using pango attributes (such as using <span color="red" /> markup)
then it wouldn't return to the default color for the rest of the
layout. pango_renderer_get_color returns NULL if there is no color
override in which case it needs to revert to the color specified as
the argument to cogl_pango_render_layout. The 'color' member of
CoglPangoRenderer has been reinstated to store that default color and
now cogl_pango_render_set_color_for_part is the only place that sets
the material color.

djdeath/clutter-android,heysion/clutter-clone,Distrotech/clutter,djdeath/clutter,kerrickstaley/clutter-vala,jigpu/clutter,jigpu/clutter,djdeath/clutter-android,tardyp/clutter,heysion/clutter-clone,Distrotech/clutter,GNOME/clutter,collects/clutter,dlespiau/clutter,jigpu/clutter,ebassi/clutter,nobled/clutter,djdeath/clutter-android,kerrickstaley/clutter-vala,rkudiyarov/clutter_osx,ebassi/clutter,djdeath/clutter-multithreaded,djdeath/clutter-android,ebassi/clutter,djdeath/clutter,spatulasnout/clutter,rkudiyarov/clutter_osx,jigpu/clutter,GNOME/clutter,kerrickstaley/clutter-vala,ebassi/clutter,rkudiyarov/clutter_osx,heysion/clutter-clone,Distrotech/clutter,djdeath/clutter-multithreaded,collects/clutter,GNOME/clutter,collects/clutter,jigpu/clutter,dlespiau/clutter,djdeath/clutter,djdeath/clutter-android,tardyp/clutter,spatulasnout/clutter,Distrotech/clutter,spatulasnout/clutter,nobled/clutter,collects/clutter,heysion/clutter-clone,spatulasnout/clutter,nobled/clutter,GNOME/clutter,collects/clutter,spatulasnout/clutter,jigpu/clutter,djdeath/clutter,ebassi/clutter,Distrotech/clutter,djdeath/clutter-multithreaded,dlespiau/clutter,kerrickstaley/clutter-vala,GNOME/clutter,rkudiyarov/clutter_osx,djdeath/clutter-multithreaded,djdeath/clutter,heysion/clutter-clone,Distrotech/clutter,djdeath/clutter,tardyp/clutter