XPshadow()
  Turn shadowing globally on/off
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   Function:   XPsetShadow()

               Using XPsetShadow(), one can turn On or Off the XPshadow()
               function, handy in those situations where shadowing is
               useless (as on Laptops, and other B/W monitors).

   Syntax:     XPsetShadow([lShadow]) --> lShadowSetting

   Arguments:  Optional, indicaties if one want Shadowing
               on, thus making XPshadow() possible, or off, thus
               making XPshadow() do nothing.

   Returns:    The previous setting. it is On by default.

   Usage:      XPsetShadow(.f.)
               * - Set's XPshadow() OFF for the rest of the Application.