Deal with liars like Rake.

We have to deal with code like this from Rake that redefines #is_a?/#kind_of?
to return a false result:

https://github.com/jimweirich/rake/blob/11a4d02eb3294244fe81cfe1d6139554d88d2d69/lib/rake/file_list.rb#L182-L186
More cleanup around fork+exec.
Added proper logging to util/thread.