Don't create the Cogl GLib source multiple times

Since the check for backend->cogl_context was accidentally moved
to clutter_backend_do_real_create_context, the Glib source that
is created at the end of clutter_backend_do_create_context() is
created and added each time create_context() is called, though
create_context() is supposed to be idempotent.

https://bugzilla.gnome.org/show_bug.cgi?id=768243

Gbp-Pq: Name Don-t-create-the-Cogl-GLib-source-multiple-times.patch

_do-not-build-cookbook

Gbp-Pq: Name 01_do-not-build-cookbook.patch

clutter-1.0 (1.26.0+dfsg-3) unstable; urgency=medium

  * Remove broken /usr/share/doc/libclutter-1.0-doc/html-cally symlink.
    (Closes: #857519)

[dgit import unpatched clutter-1.0 1.26.0+dfsg-3]

Import clutter-1.0_1.26.0+dfsg-3.debian.tar.xz

[dgit import tarball clutter-1.0 1.26.0+dfsg-3 clutter-1.0_1.26.0+dfsg-3.debian.tar.xz]

Import clutter-1.0_1.26.0+dfsg.orig.tar.xz

[dgit import orig clutter-1.0_1.26.0+dfsg.orig.tar.xz]