[lcms2] porting

here there is another step, some private functions have been imported
from lcms2, but some small changes to cietonguewidget.cpp were needed
too.

Interface is now complete (with the exception of two informational
functions), results however are still wrong and further testing is
needed (below an example).

  Digikam::CIETongueWidget::setProfile:
  lcms1: Profile white point : x= 0.312713  y= 0.32912  Y= 1
  lcms2: Profile white point : x= 0.307693  y= 0.43076  Y= 1.24611e-306

CCBUG: 294105