Update to gnome-control-center 3.6 git as of today

Most significant change is bigger sizes for the window and all icons. This is
a candidate for a version update but no bump is yet applied.

* configure.in.in: now requires x11
* src/cut-n-paste/: update code from gnome-control-center
* src/{control-center.c,gnome-control-center.c,shell.ui}: rebase on updated code
* src/patch/: update patch to current changes