Bugfix in fmpz_remove.
Bugfix in fmpz_remove.

Added a call to _fmpz_demote_val() in one case.

wbhart/flint2,fredrik-johansson/flint2,dsroche/flint2,wbhart/flint2,wbhart/flint2,fredrik-johansson/flint2,dsroche/flint2,jpflori/flint2,dsroche/flint2,fredrik-johansson/flint2,jpflori/flint2,dsroche/flint2,jpflori/flint2,jpflori/flint2