SS-3561 Single sided limits don't work

[fakemoses]

https://smath.com/bts/Issues/IssueDetail.aspx?id=3561

Description:

Due to changes in the pre-processing or argumentws, the function Lim() can't find out if x.0+0 or x.0-0 was specified as value for x. (6671)

Update(June 16, 2021):

Other options would be the use of similar symbols as exponent

Update (September 16, 2018):

In order to prevent preprocessing from destroying the side information of the limit operator, you can replace +/-0 by +/- something symbolic, which can be replaced by 0 after the limit operation.

One could also define a unit '+ and a unit '-, which could receive a special translation. Currently, this fails because Maxima does not accept operator symbols in names.