remove_all_equalities: keep removing parameter equalities until none left

remove_all_equalities: keep removing parameter equalities until none left

In e52f4ac65cbc9ce0e2b7308c4d739e12d6ba5e01 (remove_all_equalities:
keep removing equalities until no new ones are created), we made
sure newly introduced equalities were removed through variable
compression.  However, parameter compression may also introduce
new implicit equalities after simpliflying constraints, so we
may need to call compress_params several times as well.

We have to be careful, though, not to end up in an endless
loop.  We therefore need to check whether the transformation
compress_parms returns is just a translation (in which case
we can stop calling it).