GtkTextView and GtkPixelCache

[christian hergert me]

Hi Everyone,

I put up two patches on bugzilla that could use review. They add pixelcache
support for GtkTextView and add support for setting the additional cache size
of the pixel cache.

  https://bugzilla.gnome.org/show_bug.cgi?id=706728
  https://bugzilla.gnome.org/show_bug.cgi?id=701125

Thanks!

-- Christian