define propertynames() to be consistent with getproperty()

[aplavin]

No description provided.

[aplavin]

monthly bump... nightly failures are irrelevant

[nsajko]

Wait, is data a private or public property? If it's public, it should be included in propertynames(...) in any case. If it's private, you might still want to include it when the boolean argument is true.

[nsajko]

I guess the maintainers need to decide whether data is a public property.

[nsajko]

An issue with this PR is that it only overloads propertynames when getproperty is overloaded, leading to inconsistency. :data ∉ propertynames(SVector(1, 2, 3, 4)), but :data ∈ propertynames(SVector(1, 2, 3, 4, 5)). Either have both calls include :data or neither IMO.

[aplavin]

Indeed, nice catch! Fixed :data handling to be consistent.