New make target for OS X package creation.

Author: Ramakrishnan Muthukrishnan <ram@leastauthority.com>
Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Workaround for references to 'src' directory from .egg-link and .pth files.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
clean target should remove the pkg file.
misc/build_helpers/test-osx-pkg.py: script to test the OS X pkg.

After extracting the contents of the package, this script looks at the
output of 'tahoe --version-and-path' to see if the modules are installed
and invoked from the right path.

Author: Ramakrishnan Muthukrishnan <ram@leastauthority.com>
Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Delete the obsolete misc/build_helpers/test_mac_diskimage.py script.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>