Keep variables for constant zero Polynomials#81

Merged

blegat merged 5 commits intoJuliaAlgebra:masterfrom manuelbb-upb:master

Apr 9, 2021

+48-1

Commits on Mar 12, 2021

fix of issue #81 (merged commits)
manuelbb-upb
committed
1) fix of issue #79 ; also extended to work with terms
manuelbb-upb
committed
concerning #79 : Now mutating output buffer; concerning #81 : removed overspecialization of last commit - that broke tests too
manuelbb-upb
committed

Commits on Mar 15, 2021