Fix aliasing violation and out-of-bounds write in lo_permutations

[SergeevGregory]

Description

This PR fixes a critical Fortran standard violation (aliasing) in gottochblandat_sorting.f90 that causes silent heap corruption and subsequent Segmentation fault (SIGSEGV) when compiling with modern compilers (like gfortran 9.3+) under -O2 or -O3 optimization.

The Bug

In the lo_permutations subroutine, the recursive generate function takes the loop counter as a dummy argument k. However, internally it was writing to the array using the outer variable i:
pm(:,i) = permutation

Under -O2 optimization, register caching causes this to repeatedly write to pm(:,0) (an out-of-bounds write), which silently overwrites the heap descriptors and crashes the program later during deallocation.

The Fix

Changed the array index to use the correct local dummy argument:
pm(:,k) = permutation

This ensures strict compliance with the Fortran standard and completely resolves the memory corruption issue on optimized builds.

[mjv500]

Had also found this on some architectures. Thanks Gregory