var and std of complex array should return Real

[stevengj]

I noticed today with Julia 0.5 that var(rand(Complex128, 100)) gives a complex result (e.g. 0.1877618197855592 + 0.0im) even though the result is always real-valued by definition.

Furthermore, the var(iterable) definition is wrong for complex values since it is missing the requisite complex conjugations: invoke(var, (Any,), rand(Complex128, 100)) gives a completely different (complex) result (e.g. 0.02791245510174357 + 0.008222495005184707im).

The former is suboptimal, but the latter is definitely a bug.

(And the frustrating thing is that I feel like I've fixed this before, somewhere in the Julia 0.1-0.2 timeframe. If so, my fault for not putting in a regression test.)