This is because libmagic can return different results depending on
installation.
Note, this still doesn't fix all problems: smtp-entities sets md5
depending on the mime-type returned by libmagic ...
- The Makefiles now run btest with "-f diag.log" so that diangnostics
output will always be written into that file.
- Makefiles now hardcode path to btest to avoid picking up the wrong version
if in PATH.
- The canonifier scripts now live in testing/scripts, and they are
used from both btest/ and external/.
- There's a new diff-remove-uids scripts that removed connection UIDs
for diffing. The external/* tests now use that by default.
- Timestamp removal now has its own script: diff-remove-timestamps.
diff-canonifier calls that.
- All Makefile have a "brief" target that runs btest with -b.
- The higher-level directories have Makefile to call the subdirs.
