Checks Alt Key
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 Syntax

        GT_isAlt() --> lRet

 Arguments:

      None

 Returns:

      lRet    -       TRUE if ALT is being pressed, otherwise FALSE

 Description:

      Checks status of the ALT Key

 Examples:

      if GT_isAlt()
          ? "Get your grubby fingers off the ALT key."
      endif

 Source: ALT.ASM

 Author:  Andy M Leighton