Fix missing SSPRK interpolation function

Not sure how this got dropped in the move.

Author: ChrisRackauckas

lib/OrdinaryDiffEqSSPRK/src/OrdinaryDiffEqSSPRK.jl

@@ -29,7 +29,7 @@ include("addsteps.jl")
 include("functions.jl")
 
 export SSPRK53_2N2, SSPRK22, SSPRK53, SSPRK63, SSPRK83, SSPRK43, SSPRK432, SSPRKMSVS32,
-       SSPRK54, SSPRK53_2N1, SSPRK104, SSPRK932, SSPRKMSVS43, SSPRK73, SSPRK53_H, 
+       SSPRK54, SSPRK53_2N1, SSPRK104, SSPRK932, SSPRKMSVS43, SSPRK73, SSPRK53_H,
        SSPRK33, SHLDDRK_2N, KYKSSPRK42, SHLDDRK52
 
 end

lib/OrdinaryDiffEqSSPRK/src/algorithms.jl

@@ -1,6 +1,3 @@
-using OrdinaryDiffEq: explicit_rk_docstring, trivial_limiter!
-using Static: False
-
 @doc explicit_rk_docstring(
     "A third-order, five-stage explicit strong stability preserving (SSP) low-storage method.
 Fixed timestep only.",

lib/OrdinaryDiffEqSSPRK/src/interpolants.jl

@@ -123,6 +123,17 @@ end
                            c10diff2invdt2+k[1][idxs] * b10diff2invdt
 end
 
+@muladd function _ode_interpolant!(out, Θ, dt, y₀, y₁, k,
+    cache::Union{SSPRK22ConstantCache, SSPRK22Cache,
+        SSPRK33ConstantCache, SSPRK33Cache,
+        SSPRK43ConstantCache, SSPRK43Cache,
+        SSPRK432ConstantCache, SSPRK432Cache},
+    idxs, T::Type{Val{2}}, differential_vars::Nothing)
+@ssprkpre2
+@inbounds @.. broadcast=false out=(y₁[idxs] - y₀[idxs]) * c10diff2invdt2 + k[1][idxs] * b10diff2invdt
+out
+end
+
 @muladd function _ode_interpolant!(out, Θ, dt, y₀, y₁, k,
     cache::Union{SSPRK22ConstantCache, SSPRK22Cache,
         SSPRK33ConstantCache, SSPRK33Cache,