implement private in FunctionAttr2

[jeromeetienne]

• and put it in the test too

[jeromeetienne]

not that simple... in anycase this is a rare case. so do something which work even if there are constraint

[jeromeetienne]

• there is the part which is run time before and after
• but putting this function as private for a given class, it is at the declaration time

so the functionattr.private must be done at declaration time. this is the constraint

[jeromeetienne]

done