AbstractQ literal_pow (Q^2) missing

[dlfivefifty]

Base.literal_pow should be overloaded so that Q^2 works, i.e., we want the following to not error:

julia> Q = qr(randn(5,5)).Q
5×5 LinearAlgebra.QRCompactWYQ{Float64, Matrix{Float64}, Matrix{Float64}}

julia> Q*Q
5×5 Matrix{Float64}:
 -0.908458   0.15328    0.171023   0.346546    0.0431982
 -0.0574299  0.850477  -0.260641  -0.419498    0.171693
  0.0887003  0.307879   0.330109   0.0439806  -0.886813
  0.381531   0.369071   0.5402     0.521318    0.393233
  0.134058   0.148969  -0.70854    0.655912   -0.166092

julia> Q^2
ERROR: MethodError: no method matching ^(::LinearAlgebra.QRCompactWYQ{Float64, Matrix{Float64}, Matrix{Float64}}, ::Int64)

Closest candidates are:
  ^(::Regex, ::Integer)
   @ Base regex.jl:863
  ^(::Missing, ::Integer)
   @ Base missing.jl:165
  ^(::Missing, ::Number)
   @ Base missing.jl:123
  ...

Stacktrace:
 [1] literal_pow(f::typeof(^), x::LinearAlgebra.QRCompactWYQ{Float64, Matrix{Float64}, Matrix{Float64}}, ::Val{2})
   @ Base ./intfuncs.jl:351
 [2] top-level scope
   @ REPL[177]:1