Return the name of the .EXE.
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 Syntax

        GT_exename() --> cName

 Arguments:

      None

 Returns:

      cName   - The name of the EXE

 Description:

      Get the name of the exe file ran up
      Reads the PSP segment to find the executable name.

 Examples:

      ? "Currently running " + GT_exename()

 Source: EXENAME.C

 Author:  Andy M Leighton