Add support for Supr key

Add support for Supr key

    Del : Delete character under cursor.
    Shift + Del : Delete the line under cursor.
    Ctrl + Del: Delete the full screen.
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 config.def.h |   16 ++++++++++++----
 st.info      |    2 ++
 2 files changed, 14 insertions(+), 4 deletions(-)