The intent of this target is to run our test suite against the installed jre.
This should help prevent our VM from diverging in implementation from the jdk.
The remainder of this commit fixes the problems that this exposes.
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.
