Comparison between quantities with different underlying number type

[dojt]

I think I may have found a bug somewhere in the defs of == and <. If the underlying number types on LHS and RHS differ, then == and < don't behave consistently.

Example:

julia> 1//10 < 0.1
true
julia> (1//10)s <= 0.1s
false
julia> (1//10)s >= 0.1s
false

The first comparison is correct, as 0.1::Float64 === 0.1000000000000000055511151231257827021181583404541015625. Obviously, at least one of the other two inequalities is wrong.

The problem seems to be that < promotes to Float64, but == doesn't, so < will conclude the two values are equal, wheres == will conclude that they're not.

julia> @code_lowered  ==(  (1//10)s, 0.1s  )

julia> @code_lowered  Unitful._lt(  (1//10)s, 0.1s  )

[sostock]

Related: #399