Previously, I used a shell script to extract modification date ranges
from the Git history, but that was complicated and unreliable, so now
every file just gets the same year range in its copyright header. If
someone needs to know when a specific file was modified and by whom,
they can look at the Git history themselves; no need to include it
redundantly in the header.
This commit introduced conditional includes which is not the preferred
method. Will do it in the makefile instead.
This reverts commit 7148556979793c56e69dabf7e31813930a0e979a.
