Remove vcat(::MatElem, ::MatElem) and hcat(::MatElem, ::MatElem)

These methods are never called because there are
`vcat(::MatrixElem{T}...) where T <: NCRingElement`
`hcat(::MatrixElem{T}...) where T <: NCRingElement`

src/Matrix.jl

@@ -6107,50 +6107,6 @@ end
 #
 ###############################################################################
 
-@doc raw"""
-    hcat(a::MatElem, b::MatElem)
-
-Return the horizontal concatenation of $a$ and $b$. Assumes that the
-number of rows is the same in $a$ and $b$.
-"""
-function hcat(a::MatElem, b::MatElem)
-   nrows(a) != nrows(b) && error("Incompatible number of nrows in hcat")
-   c = similar(a, nrows(a), ncols(a) + ncols(b))
-   n = ncols(a)
-   for i = 1:nrows(a)
-      for j = 1:ncols(a)
-         c[i, j] = a[i, j]
-      end
-      for j = 1:ncols(b)
-         c[i, n + j] = b[i, j]
-      end
-   end
-   return c
-end
-
-@doc raw"""
-    vcat(a::MatElem, b::MatElem)
-
-Return the vertical concatenation of $a$ and $b$. Assumes that the
-number of columns is the same in $a$ and $b$.
-"""
-function vcat(a::MatElem, b::MatElem)
-   ncols(a) != ncols(b) && error("Incompatible number of columns in vcat")
-   c = similar(a, nrows(a) + nrows(b), ncols(a))
-   n = nrows(a)
-   for i = 1:nrows(a)
-      for j = 1:ncols(a)
-         c[i, j] = a[i, j]
-      end
-   end
-   for i = 1:nrows(b)
-      for j = 1:ncols(a)
-         c[n + i, j] = b[i, j]
-      end
-   end
-   return c
-end
-
 @doc raw"""
     vcat(A::MatrixElem{T}...) where T <: NCRingElement -> MatrixElem