Log Message:
Update to 0.1.52

Changelog:
2018-06-02 babl-0.1.52
Concurrency fixes and fixes to handling of 0/1 entry palettes, do not
pre-equalize XYZ conversion matrices for sRGB, internal clean-ups, pre-define
ACES2065-1 and ACEScg BablSpaces, add R~G~B~ set of spaces, which for all
BablSpaces mean use sRGB TRC.