Update the RELEASING notes

(cherry picked from commit 2ce521afad01e95d072f5e069c392615bce15b1d)
kms: add public API to override the default configuration of outputs

Add API to allow complex applications using the KMS backend
to go almost straight to direct configuration (which is not possible
because Cogl needs to be in charge of buffers and FB objects).

https://bugzilla.gnome.org/show_bug.cgi?id=705837

Reviewed-by: Robert Bragg <robert@linux.intel.com>

(cherry picked from commit 52fb8e1c33d8c83c731c05cee767928fdd5991d7)