Clears many gcc warnings of the form:

uvY.c: In function ‘XcmsCIEuvYToCIEXYZ’:
uvY.c:263:19: warning: comparison between signed and unsigned integer
  expressions [-Wsign-compare]
     for (i = 0; i < nColors; i++, pColor++) {
                   ^
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>