* lab_tetra squashed

* initial version is almost written

* unfinished work

* compilation fixed, to be debugged

* Lab test removed

* more fixes

* Luv2RGBinteger: channels order fixed

* Lab structs removed

* good trilinear interpolation added

* several fixes

* removed Luv2RGB interpolations, XYZ tables; 8-cell LUT added

* no_interpolate made 8-cell

* interpolations rewritten to 8-cell, minor fixes

* packed interpolation added for RGB2Luv

* tetra implemented

* removing unnecessary code

* LUT building merged

* changes ported to color.cpp

* minor fixes; try to suppress warnings

* fixed v range of Luv

* fixed incorrect src channel number

* minor fixes

* preliminary version of Luv2RGBinteger is done

* Luv2RGB_b is in progress

* XYZ color constants converted to softfloat

* Luv test: precision fixed

* Luv bit-exactness test added

* warnings fixed

* compilation fixed, error message fixed

* Luv check is limited to [0-2,0-2,0-2] by XYZ

* L->Y generation moved to LUT

* LUTs added for up and vp of Luv2RGB_b

* still works

* fixed-point is done, works at maxerr 2

* vectorized code is done, 2x slower than original

* perf improved by 10%

* extra comments removed

* code moved to color.cpp

* test_lab.cpp updated

* minor refactoring

* test added for Luv2RGB

* OCL Luv2RGB_b: XYZ are limited to [0, 2]; docs updated

* Luv2RGB_b rewritten to universal intrinsics

* test_lab.cpp moved to luv_tetra branch