XPclr2attr()
  Convert a Clipper color string to an Attribute
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   Function:   XPclr2attr()

               Converts a Clipper Color string to an Attribute, as used
               by some of the Expand Library functions. Note that
               only 1 color is converted, and thus only one color
               attribute is returned. use an Array and XPaDelimit()
               for instance, to decode the full SetColor() string.
               (as used alsewhere in the Library).

               Note that this function is Assembly written, and thus fast
               enough for frequently used routines.

   Syntax:     XPclr2attr(cColor) --> nAttr

   Arguments:  cColor is a Clipper color String.

   Returns:    nAttr is a screen Attribute.

   Usage:      XPclr2attr("W+/N") returns 15
               XPclr2attr("U+") returns 9..