This also installs symlinks from "zeek" and "bro-config" to a wrapper
script that prints a deprecation warning.
The btests pass, but this is still WIP. broctl renaming is still
missing.
#239
- Give Dir::monitor() a param for the polling interval, so different
dirs can be monitored at different frequencies.
- Fix race in Exec::run() when reading extra output files produced by
a process -- it was possible for Exec::run() to return before all
extra output files had been fully read.
- Add test cases.
