Define dataids for a BandedMatrix (#472)

Author: jishnub

src/banded/BandedMatrix.jl

@@ -30,6 +30,7 @@ end
 _BandedMatrix(data::AbstractMatrix, m::Integer, l, u) = _BandedMatrix(data, oneto(m), l, u)
 
 Base.parent(B::BandedMatrix) = B.data
+Base.dataids(B::BandedMatrix) = (Base.dataids(B.data)..., Base.dataids(B.raxis)...)
 
 const DefaultBandedMatrix{T} = BandedMatrix{T,Matrix{T},OneTo{Int}}
 
@@ -1030,4 +1031,4 @@ function one(A::BandedMatrix)
     m,n = size(A)
     m==n || throw(DimensionMismatch("multiplicative identity defined only for square matrices"))
     typeof(A)(I, (m,n))
-end
+end