build-sys: move sphinx output to docs/python-systemd

And on fd.o it goes into a dir parallel to man/.
man/*.html: link to directives, python, guvev, libudev in headers

Since the HTML files are in different directories during build
and on fd.o, links are broken in the build directory. This could
be fixed by moving stuff around, or by modifying the files during
upload, but I think that people do not usually create HTML files
for local browsing, and this is not necessary.
systemd-python: fix typos
systemd-python: fix segfault on double close
Revert "bootchart: use _cleanup_close_"

This reverts commit 0ea9530d401827e299c6e04a433e69a7a2a89d80.

attribute(cleanup) can only be used inside functions (*of, sysfd
are leaked).

Cleanup functions are only called once when exiting scope (*f
is leaked twice).