Log Message:
babl: Update to 0.1.72

2019-08-22 babl-0.1.72
Added handling for grayscale ICC profiles and gobject introspection support.
Optimizations for many format conversions for u8, u16 and half formats. And
fixed a crash for NANs in float to u8 conversions.

2019-08-02 babl-0.1.70
Build fixes making the meson build work with more architectures.

2019-07-25 babl-0.1.68
Added Yu'v' (CIE 1976 UCS) color model.  Fixed a severe non-initialised memory
issue - that kept us from using fast paths for many babl spaces loaded from
profile. More fully symmetric conversions between associated and separate
alpha. Added more converters, both SSE2 and non-SSE2 for matrix-conversion
between different RGB spaces.  Improvements to website/documentation; babl is
now using the terms associated alpha and separate alpha, all of:
nonpremultiplied-, premultiplied- and nonassociated- alpha are now considered
deprecated API. HCY luminance is now relative to the RGB space used - no change
for sRGB related pixel formats. AVX2 acceleration for some linear to float
conversions.