port 2P step 1: vendor CPython 2.7.18 as the mtpython static library

The embedded 40250 script layer needs its own interpreter on five platforms.
2.7 is end-of-life, so nothing can be fetched from the target SDKs and the
source is vendored (official 2.7.18 tarball, trimmed to 25MB; Lib/ stays for
step 3's python27.zip).

cpython-2.7.18/CMakeLists.txt builds one `mtpython` static library from exactly
the 133 objects the reference libpython2.7.a contains, off by default behind
-DMTGODOT_EMBED_PYTHON=ON. The source list and the built-in module table
(config/config.c, 39 entries) are shared; pyconfig.h is a probe result and is
not, so each platform keeps its own under config/<platform>/, regenerated by
tools/py_embed/gen_pyconfig.sh and checked against the shared table.

Three vendor patches, documented in docs/THIRD-PARTY.md: configure/configure.ac
learn arm64 on macOS, and posixmodule.c undefines the process-control calls it
hard-defines past pyconfig.h when building for iOS.

macOS (ctest python.embed: every builtin imports, codecs and pickle work off the
vendored Lib/), Android arm64 and iOS arm64 build. Linux needs a Linux host and
Windows needs a MinGW-vs-MSVC decision; both are noted for step 4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

extension/third_party/cpython-2.7.18/Lib/distutils/command/command_template

@@ -0,0 +1,45 @@
+"""distutils.command.x
+
+Implements the Distutils 'x' command.
+"""
+
+# created 2000/mm/dd, John Doe
+
+__revision__ = "$Id$"
+
+from distutils.core import Command
+
+
+class x (Command):
+
+    # Brief (40-50 characters) description of the command
+    description = ""
+
+    # List of option tuples: long name, short name (None if no short
+    # name), and help string.
+    user_options = [('', '',
+                     ""),
+                   ]
+
+
+    def initialize_options (self):
+        self. = None
+        self. = None
+        self. = None
+
+    # initialize_options()
+
+
+    def finalize_options (self):
+        if self.x is None:
+            self.x = 
+
+    # finalize_options()
+
+
+    def run (self):
+
+
+    # run()
+
+# class x