Function: srepr does not include assumptions

[cklb]

Similar to PR #8819 which added support for assumptions in Symbol, the same ability would be really helpful for Function. If I understand #6494 correctly, Assumptions themselves should work for Function since 6b5a397.

Sadly, currently the following assertion fails:

x = Function('x', negative=0, integer=1)
assert eval(srepr(x)) == x

If I correctly understand the changes in #8819, _print_FunctionClass in printing/repr.py has to extended to provide these information.

If someone could provide a little insight to the involved assumptions system I would happily try to add the missing lines.