moving COLR stuff to separate header file?

[Werner LEMBERG]

Dominik,


while comparing the current git with the last release to check
differences, I noticed that the COLR stuff is quite large.  IMHO, it
deserves to be moved into a separate file.  What do you think?  If you
agree, can you do that?

I can imagine to move COLR stuff into `ftcolor.h` so that this file
covers both CPAL and COLR functionality.


    Werner