Added test for scalar_addmul_si,
Added test for scalar_addmul_si,

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