Log Message:
Update to 0.1.60

Changelog:
2018-10-05 babl-0.1.60                                              \ 
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Improved thread safety, acceleration for R'G'B'A u8 -> cairo-ARGB32 conversion.
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2018-10-05 babl-0.1.58                                              \ 
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Preserve color of transparent pixels in conversion to premultiplied alpha,
Added single precision code-paths for faster fallback/reference conversions.
New BABL_ICC_INTENT_PERFORMANCE bitflag for combining with intent as bitflags,
use of matrix+trc when relative colorimetric CLUT is present. New color model
and formats, CIE xyY.