Adding a PartFinalizer that runs a commmand at the completion of each
test part.
Adding an option -n to btest-rst-cmd that truncates output longer than N
lines.
New "Sphinx-mode" for BTest, activated with -S.

This allows to capture a test's diagnostic output when running from
inside Sphinx; the output will now be inserted into the generated
document.

Also, when running from inside Sphinx, we no longer do the btest-diff
check of the output; that now happens only when running externally
from within the test suite.
Merge branch 'master' of ssh://git.bro-ids.org/btest
Test portability fix.

A hack, really.