Also applied to profiles.
This will of course slow down slightly the current histograms. On the other hand, they should be replaced at some stage with the new ROOT7 ones, so this is kind of temporary

See merge request gaudi/Gaudi!820

See merge request gaudi/Gaudi!812

they help with debugging

if a .new file already exists, use an incremental new name

use add_custom_command DEPFILE argument for Ninja and IMPLICIT_DEPENDS 
for Makefile