Add setting to invoke page up/page down on scrollbars clicks
Add setting to invoke page up/page down on scrollbars clicks

The default value of 'gtk-primary-button-warps-slider' in GTK+3 is
True[1] and in GTK+2 is False[2].  This patch sets the setting to
False in GTK+3 to keep the same behaviour as before.

[1] http://developer.gnome.org/gtk3/stable/GtkSettings.html#GtkSettings--gtk-primary-button-warps-slider
[2] http://developer.gnome.org/gtk/2.24/GtkSettings.html#GtkSettings--gtk-primary-button-warps-slider

Patch for sugar provided by Manuel Kaufmann and ported to artwork.

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

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