so the tests work when run from an install directory.
They are currently skipped on the daily runs (not from the buildbots)
for checking refleaks, etc.

in r62788.

The new mac-specific functions must be ignored.

which clears them at the end.

This patch removes the dependency on the Carbon package from urllib.
The mac-specific code for getting proxy configuration is now writting in
Python using ctypes and uses the SystemConfiguration framework instead of
InternetConfig. Also provides a mac-specific implementation of proxy_bypass.

The 'mac' platform (that is, os.name == 'mac') was used for the MacOS 9 port,
which is no longer supported (as of Python 2.4 IIRC).