Update Ceres to 1.5RC3

It brings optimization of DENSE_QR and DENSE_SCHUR solvers.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55049 954f8c5b-7b00-dc11-b283-0030488c597c
Switch from DENSE_NORMAL_CHOLESKY to DENSE_QR

DENSE_QR is better behaved numerically and after recent
changes from Sameer there's no big difference in speed.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55050 954f8c5b-7b00-dc11-b283-0030488c597c