This commit is the result of running the gdb/copyright.py script,
which automated the update of the copyright year range for all
source files managed by the GDB project to be updated to include
year 2023.

New in this version:

 - Rebase on master, fix a few more issues that appeared.

python-internal.h contains a number of macros that helped make the code
work with both Python 2 and 3.  Remove them and adjust the code to use
the Python 3 functions.

Change-Id: I99a3d80067fb2d65de4f69f6473ba6ffd16efb2d

New in this version:

 - Add a PY_MAJOR_VERSION check in configure.ac / AC_TRY_LIBPYTHON.  If
   the user passes --with-python=python2, this will cause a configure
   failure saying that GDB only supports Python 3.

Support for Python 2 is a maintenance burden for any patches touching
Python support.  Among others, the differences between Python 2 and 3
string and integer types are subtle.  It requires a lot of effort and
thinking to get something that behaves correctly on both.  And that's if
the author and reviewer of the patch even remember to test with Python
2.

See this thread for an example:

  https://sourceware.org/pipermail/gdb-patches/2021-December/184260.html

So, remove Python 2 support.  Update the documentation to state that GDB
can be built against Python 3 (as opposed to Python 2 or 3).

Update all the spots that use:

 - sys.version_info
 - IS_PY3K
 - PY_MAJOR_VERSION
 - gdb_py_is_py3k

... to only keep the Python 3 portions and drop the use of some
now-removed compatibility macros.

I did not update the configure script more than just removing the
explicit references to Python 2.  We could maybe do more there, like
check the Python version and reject it if that version is not
supported.  Otherwise (with this patch), things will only fail at
compile time, so it won't really be clear to the user that they are
trying to use an unsupported Python version.  But I'm a bit lost in the
configure code that checks for Python, so I kept that for later.

Change-Id: I75b0f79c148afbe3c07ac664cfa9cade052c0c62

Currently, gdb's Python layer captures the current architecture and
language when "entering" Python code.  This has some undesirable
effects, and so this series changes how this is handled.

First, there is code like this:

  gdbpy_enter enter_py (python_gdbarch, python_language);

This is incorrect, because both of these are NULL when not otherwise
assigned.  This can cause crashes in some cases -- I've added one to
the test suite.  (Note that this crasher is just an example, other
ones along the same lines are possible.)

Second, when the language is captured in this way, it means that
Python code cannot affect the current language for its own purposes.
It's reasonable to want to write code like this:

    gdb.execute('set language mumble')
    ... stuff using the current language
    gdb.execute('set language previous-value')

However, this won't actually work, because the language is captured on
entry.  I've added a test to show this as well.

This patch changes gdb to try to avoid capturing the current values.
The Python concept of the current gdbarch is only set in those few
cases where a non-default value is computed or needed; and the
language is not captured at all -- instead, in the cases where it's
required, the current language is temporarily changed.

This commit brings all the changes made by running gdb/copyright.py
as per GDB's Start of New Year Procedure.

For the avoidance of doubt, all changes in this commits were
performed by the script.

In a future commit I'm going to be creating gdb.Membuf objects from a
new file within gdb/python/py*.c.  Currently all gdb.Membuf objects
are created directly within infpy_read_memory (as a result of calling
gdb.Inferior.read_memory()).

Initially I split out the Membuf creation code into a new function,
and left the new function in gdb/python/py-inferior.c, however, it
felt a little random that the Membuf creation code should live with
the inferior handling code.

So, then I moved all of the Membuf related code out into a new file,
gdb/python/py-membuf.c, the interface is gdbpy_buffer_to_membuf, which
wraps an array of bytes into a gdb.Membuf object.

Most of the code is moved directly from py-inferior.c with only minor
tweaks to layout and replacing NULL with nullptr, hence, I've left the
copyright date on py-membuf.c as 2009-2021 to match py-inferior.c.

Currently, the only user of this code is still py-inferior.c, but in
later commits this will change.

There should be no user visible changes after this commit.