type inference of && and || chains

[StefanKarpinski]

Although I fixed #5084 by using a trinary operator (which is better style anyway, imo), type inference on the short-circuit && and || operators could be tighter:

julia> f(b::Bool) = b && error("nope") || 1
f (generic function with 1 method)

julia> code_typed(f,(Bool,))
1-element Array{Any,1}:
 :($(Expr(:lambda, {:b}, {{:#s2},{{:b,Bool,0},{:#s2,Bool,2}},{}}, quote  # none, line 1:
        unless b::Bool goto 0
        #s2 = throw($(Expr(:new, :(top(getfield)($(Base),:ErrorException)::Type{ErrorException}), "nope"))::ErrorException)::None
        goto 1
        0:
        #s2 = false
        1:
        unless #s2::Bool goto 2
        return #s2::Bool
        2:
        return 1
    end)))

julia> f(true)
ERROR: nope
 in f at none:1

julia> f(false)
1

This can only ever return an Int and we could definitely infer that.

[JeffBezanson]

should be helped by #5560