Message 64208 - Python tracker

This patch adds a new get_data function to the pkgutil module, allowing
access to data stored in the package directory. It wraps the PEP 302
loader "get_data" function, so that it works with such loaders (for
example, zipimport).

The patch includes documentation and tests (I created a new test_pkgutil
test module, but did not add tests for the existing pkgutil functionality).

All tests pass on Windows against svn rev 61679 (except test_tcl, which
was skipped as I didn't build TCL support).