tw_TFile( fHndl, tp, lt, bt, rt, j, norm )
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     Displays an open textfile in a screen region and handles
     navigation through the file by keypresses. This function is called
     by twTextFile().

     ACTIVE KEYS:

     Down          - Down one line
     Up            - Up one line
     Left          - Left one column
     Right         - Right one column
     Home          - Left hand margin
     End           - Right hand margin
     PageUp        - Up one page
     PageDown      - Down one page
     Ctrl PageUp   - Top of file
     Ctrl PageDown - Bottom of file
     Escape        - Abort display

       Arguments:

     fHndl - 'N' File handle.

     tp,lt
     bt,rt - 'N' Screen coordinates for text display.

     j     - 'N' lines offset into file to start.

     norm  - 'N' DOS Colour attribute for display.

       Return:

     0 if all OK.
     8 if memory allocation error occurred.

       Example:

     tw_TFile( nHandle, wT + 1, wL + 1, wB - 1, ;
                    wR - 1, 1, fbColor )