Converts Clipper colour string to numeric attribute
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 Syntax

       GT_ColorToN(<cColourString>) --> <nAttribute>

 Arguments:

     <cColourString> is the Clipper colour string to convert to an
                     numeric attribute

 Returns:

     NIL

 Description:

     Converts a Clipper colour string into an attribute numeric.  It only
     looks at the first parameter of the string.  ie:

     nAttribute := GT_ColorToN("W+/B,N/W")
                             ↑↑↑↑-This is used

     Note: The module also includes a C/ASM callable function equivelant
           in the form of:

              void int gt_ColorToN (char *string);

 Examples:

     nAttribute := GT_ColorToN("W+/B")     // Result: 31

 Source: COLORTON.C

 Author:  Ian 'DrDebug' Day (Dark Black Software Ltd)