gifIsGIF()

         Indicates if a file has GIF format or not

    Syntax:

         gifIsGIF ( cFile ) -> lIsGIF

         cFile : Name of the GIF file

    Description:

         This function returns a logic indicating if the file is GIF or not.
         The rest of GIF functions use this function to decide when to
         return some value.

    Return:

         .T. if the file is GIF or .F. if it does not have GIF format or
         does not exist.

    Example:

         ? gifIsGIF ( "c:\xx\giveme.gif" )