Patch was merged in [1]. It's not going to make into any 1.19.x releases, but most probably will be included in 1.20.x. (I'm talking about X.Org, not xcalib). Then xcalib should work again.
[1] https://cgit.freedesktop.org/xorg/xserver/commit/?id=ac138f9b31b0fba00742edbc3326afe66e28099a
