Fix building Matrix of poly and matpoly of same eltype

Author: blegat

src/poly.jl

@@ -155,6 +155,7 @@ Base.convert{C}(::Type{PolyType{C}}, p::TermContainer{C}) = p
 
 # needed to build [p Q; Q p] where p is a polynomial and Q is a matpolynomial in Julia v0.5
 Base.convert{C}(::Type{TermType{C}}, p::TermContainer{C}) = p
+Base.convert{C, T}(::Type{TermType{C, T}}, p::TermContainer{C, T}) = p
 
 function Base.convert{S}(::Type{S}, p::TermContainer)
     s = zero(S)

test/poly.jl

@@ -135,8 +135,10 @@
         @test typeof(MultivariatePolynomials.TermContainer{true, Int}(p)) == Polynomial{true, Int}
         p = x + y
         Q = MatPolynomial([true false; false true], [x, y])
+        P = MatPolynomial([1 2; 2 1], [x, y])
         @test isa([p, Q], Vector{Polynomial{true, Int}})
         @test isa([p Q; Q p], Matrix{Polynomial{true, Int}})
+        @test isa([p P; P 0], Matrix{Polynomial{true, Int}})
     end
     @testset "Non-commutative MatPolynomial" begin
         @ncpolyvar x y