Add digamma for CPU + CUDA.  Includes tests.
diff --git a/Eigen/src/Core/arch/CUDA/PacketMath.h b/Eigen/src/Core/arch/CUDA/PacketMath.h
index 9d57731..d3d9f91 100644
--- a/Eigen/src/Core/arch/CUDA/PacketMath.h
+++ b/Eigen/src/Core/arch/CUDA/PacketMath.h
@@ -40,6 +40,7 @@
     HasSqrt = 1,
     HasRsqrt = 1,
     HasLGamma = 1,
+    HasDiGamma = 1,
     HasErf = 1,
     HasErfc = 1,
 
@@ -63,6 +64,7 @@
     HasSqrt = 1,
     HasRsqrt = 1,
     HasLGamma = 1,
+    HasDiGamma = 1,
     HasErf = 1,
     HasErfc = 1,