All code (util.byte_compile, build_py, install_lib) can now create .pyc
and/or.pyo files according to options given by users, without
interference from the calling Python?s own optimize mode or from the
sys.dont_write_bytecode switch.

The rationale is that packaging gives control over the creation of
.pyc/.pyo files to the user with its own explicit option, and the
behavior should not be changed if the calling Python happens to run with
-B or -O for whatever reason.

This is actually a bug fix, not an improvement: Digging into the early
history of distutils shows that the original author wanted this behavior
(see for example comments in build_py in r12940).

Logging calls have the signature (msg, *args, **kwargs) so that the
%-formatting can be delayed until it is needed.  Logger objects also have an
isEnabledFor method that can be used to isolate expensive code.

Next steps: use only one of d2.logger methods or logging module functions;
use a proper handler in our test machinery instead of monkey-patching; remove
cmd.warn and cmd.announce and use logging instead.  TODOs have been added in
the modules and on the wiki.

The goal is to avoid overlaps between commands and scripts names (for
instance the "install" script and the "install" command)