Fix incorrect promotion in bidiagonal backslash.

Author: Sacha0

base/linalg/bidiag.jl

@@ -263,7 +263,7 @@ function naivesub!{T}(A::Bidiagonal{T}, b::AbstractVector, x::AbstractVector = b
 end
 
 function \{T,S}(A::Bidiagonal{T}, B::AbstractVecOrMat{S})
-    TS = typeof(zero(T)*zero(S) + zero(T)*zero(S))
+    TS = typeof((zero(T)*zero(S) + zero(T)*zero(S))/one(T))
     TS == S ? A_ldiv_B!(A, copy(B)) : A_ldiv_B!(A, convert(AbstractArray{TS}, B))
 end