Improve byte-compilation in packaging to be independent of -O or -B.

The code I fixed to comply with PEP 3147 still had one bug: When run
under python -O, some paths for pyc files would be pyo, because I called
imp.cache_from_source without explicit debug_override argument in some
places, and under -O that would return .pyo (this is well explained in
the imp docs).  Now all code (util.byte_compile, build_py, install_lib)
can create .pyo files according to options given by users,
without interference from the calling Python’s own optimize mode.

On a related topic, I also removed the code that prevented byte
compilation under python -B.  The rationale is that packaging gives
control over the creation of pyc 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 for whatever reason.  I will argue that this is a
bug fix and ask to be allowed to backport this change to distutils.

Finally, I moved one nugget of information about the --compile and
--optimize options from the source into the doc.  It clears up a
misunderstanding that I (and maybe other people) had.

Doc/library/packaging.util.rst

@@ -116,7 +116,6 @@ This module contains various helpers for the other modules.
    values are ``n``, ``no``, ``f``, ``false``, ``off`` and ``0``.  Raises
    :exc:`ValueError` if *val* is anything else.
 
-.. TODO Add :term: markup to bytecode when merging into the stdlib
 
 .. function:: byte_compile(py_files[, optimize=0, force=0, prefix=None, base_dir=None, verbose=1, dry_run=0, direct=None])
 
@@ -134,7 +133,7 @@ This module contains various helpers for the other modules.
 
    If *force* is true, all files are recompiled regardless of timestamps.
 
-   The source filename encoded in each bytecode file defaults to the filenames
+   The source filename encoded in each :term:`bytecode` file defaults to the filenames
    listed in *py_files*; you can modify these with *prefix* and *basedir*.
    *prefix* is a string that will be stripped off of each source filename, and
    *base_dir* is a directory name that will be prepended (after *prefix* is
@@ -150,3 +149,6 @@ This module contains various helpers for the other modules.
    figure out to use direct compilation or not (see the source for details).
    The *direct* flag is used by the script generated in indirect mode; unless
    you know what you're doing, leave it set to ``None``.
+
+   This function is independent from the running Python's :option:`-O` or
+   :option:`-B` options; it is fully controlled by the parameters passed in.

Doc/packaging/builtdist.rst

@@ -164,9 +164,7 @@ will reflect this and now has the form :file:`foo-1.0.win32-py2.0.exe`.  You
 have to create a separate installer for every Python version you want to
 support.
 
-.. TODO Add :term: markup to bytecode when merging into the stdlib
-
-The installer will try to compile pure modules into bytecode after installation
+The installer will try to compile pure modules into :term:`bytecode` after installation
 on the target system in normal and optimizing mode.  If you don't want this to
 happen for some reason, you can run the :command:`bdist_wininst` command with
 the :option:`--no-target-compile` and/or the :option:`--no-target-optimize`

Doc/packaging/commandref.rst

@@ -115,7 +115,24 @@ Build C/C++ extension modules.
 -------------------
 
 Build the Python modules (just copy them to the build directory) and
-byte-compile them to .pyc files.
+:term:`byte-compile <bytecode>` them to :file:`.pyc` and/or :file:`.pyo` files.
+
+The byte compilation is controlled by two sets of options:
+
+- ``--compile`` and ``--no-compile`` are used to control the creation of
+  :file:`.pyc` files; the default is ``--no-compile``.
+
+- ``--optimize N`` (or ``-ON``) is used to control the creation of :file:`.pyo`
+  files: ``-O1`` turns on basic optimizations, ``-O2`` also discards docstrings,
+  ``-O0`` does not create :file:`.pyo` files; the default is ``-O0``.
+
+You can mix and match these options: for example, ``--no-compile --optimize 2``
+will create :file:`.pyo` files but no :file:`.pyc` files.
+
+.. XXX these option roles do not work
+
+Calling Python with :option:`-O` or :option:`-B` does not control the creation
+of bytecode files, only the options described above do.
 
 
 :command:`build_scripts`
@@ -341,7 +358,14 @@ Install C/C++ header files.
 :command:`install_lib`
 ----------------------
 
-Install C library files.
+Install all modules (extensions and pure Python).
+
+.. XXX what about C libraries created with build_clib?
+
+Similarly to ``build_py``, there are options to control the compilation of
+Python code to :term:`bytecode` files (see above).  By default, :file:`.pyc`
+files will be created (``--compile``) and :file:`.pyo` files will not
+(``--optimize 0``).
 
 
 :command:`install_scripts`