Short representation for LWB and UPB

[Jose E. Marchesi]

Hello people!

I am thinking about a potential shorter representation of the UPB and
LWB operators monadic and dyadic operators on rows.

In SUPPER stropping in many (most?) cases both LWB and UPB require at
least five characters. It would be nice to support a shorter
non-bold representation like we did with `of'.

Ideas:

  <<a and 2<<a for `LWB a' and `2 LWB a' respectively.
  >>a and 2>>a for `UPB a' and `2 UPB a' respectively.

  /<a and 2/<a    ''
  \\a and 2//a    ''

  -<a and 2-<a    ''
  +<a and 2+<a    ''

  -/a and 2-/a    ''
  +/a and 2+/a    ''

Reminder:

  monads: %^&+-~!?
  nomads: ></=*

Thoughts?