Set background color to GtkTreeView - SL #3962
Set background color to GtkTreeView - SL #3962

This makes the treeview header get the same style as in GTK+2.  The
background is the same color as the header button, so looks a
rectagular area.  And a white round border is visible when the button
is active.

Signed-off-by: Manuel Quiñones <6f5069c5b6be23302a13accec56587944be09079@laptop.org>
Acked-by: Simon Schampijer <088e16a1019277b15d58faf0541e11910eb756f6@laptop.org>

sugarlabs/sugar-artwork,gusDuarte/sugar-artwork,ceibal-tatu/sugar-artwork,i5o/sugar-artwork,i5o/sugar-artwork,godiard/sugar-artwork,tchx84/debian-pkg-sugar-artwork,sugarlabs/sugar-artwork,godiard/sugar-artwork,sugarlabs/sugar-artwork,tchx84/debian-pkg-sugar-artwork,godiard/sugar-artwork,samdroid-apps/sugar-artwork,tchx84/debian-pkg-sugar-artwork,samdroid-apps/sugar-artwork,gusDuarte/sugar-artwork,gusDuarte/sugar-artwork,gusDuarte/sugar-artwork,i5o/sugar-artwork,samdroid-apps/sugar-artwork,ceibal-tatu/sugar-artwork,ceibal-tatu/sugar-artwork