roundup / down `Irrational` endpoints

[dlfivefifty]

I propose that a .. b should round a down and b up if they are irrational, so that a in a..b and b in a..b is always true. This would fix the following:

julia> π in 0..π
false

julia> π in (0..Float64(π, RoundUp))
true

[hyrodium]

The following property should also hold, so RoundUp/RoundDown should be optional.

julia> a = 1
1

julia> b = pi
π = 3.1415926535897...

julia> c = 4
4

julia> rightendpoint(a..b) == leftendpoint(b..c)
true

Maybe, defining @correctbounds macro would be helpful?

julia> 0..π
0.0..3.141592653589793

julia> @correctbounds 0..π
0.0..3.1415926535897936

julia> @correctbounds OpenInterval(0,π)
0.0..3.141592653589793

[hyrodium]

Here's another example with Rational

julia> 0.0 .. 1//3
0.0 .. 0.3333333333333333

julia> 1//3 in 0.0 .. 1//3
false