== not transitive for TypeVars

[jiahao]

Admittedly I don't really grok how TypeVars can be used at the user level, but I find this rather unintuitive:

julia> A = TypeVar(:x, Integer, Real); B = TypeVar(:x, FloatingPoint, Real); C = Real;

julia> A==B #false?
false

julia> B==C #false?
true

julia> C==A #false?
true

[JeffBezanson]

Covered by #8974. Also TypeVars should not be created manually, and in the future that will probably be even more important.

[JeffBezanson]

fixed by 3074b70