Fixes three errors obtained by valgrind+verrou - round2

Description

Fixes three errors obtained by valgrind+verrou - round2

This contains :

• a fix to avoid overflows, introduced in the previous merge request
• a fix for CG energy difference, which was computed from the new eigenenergy and not the old one
• a fix for 1D-0D FFT kernel which switched between two branching using an exact floating point comparison.

News snippet

Further small bugfixes related to numerical instabilities

Checklist

• I have checked that my code follows the Octopus coding standards