[PATCH] Hal privilige seperation

[David Zeuthen]

Hi,

I made a few more changes. The runner now searches $PATH for the program
to invoke before checking /usr/libexec/ and /usr/share/hal/scripts -
this should be safe as $PATH isn't tampered with on startup. Needed to
pass $PATH for hald to the runner. It also has the feature that it
doesn't break run-hald.sh and debug-hald.sh which are useful for
development. 

Also, after some debugging, fixed a bug where we free elements in the
errors array in hald_exec_method_cb when a method throws an exception.

I may have commit other fixes too but probably not as serious as the
first one.

    David