Increase numerical threshold for test_mean

The two tests slightly exceeding the threshold from 1000*epsilion(1._dp):
1. sum( abs( mean(cd3,2) - sum(cd3,2)/real(size(cd3,2), dp) ))
2. sum( abs( mean(d4,2) - sum(d4,2)/real(size(d4,2), dp) ))

Author: awvwgk

src/tests/stats/test_mean.f90

@@ -7,7 +7,7 @@ program test_mean
 implicit none
 
 real(sp), parameter :: sptol = 1000 * epsilon(1._sp)
-real(dp), parameter :: dptol = 1000 * epsilon(1._dp)
+real(dp), parameter :: dptol = 2000 * epsilon(1._dp)
 
 real(sp) :: s1(3) = [1.0_sp, 2.0_sp, 3.0_sp]