Add initialiser to C++ class for fmpz's.
Add initialiser to C++ class for fmpz's.

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