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/bisect.py

@@ -0,0 +1,92 @@
+"""Bisection algorithms."""
+
+def insort_right(a, x, lo=0, hi=None):
+    """Insert item x in list a, and keep it sorted assuming a is sorted.
+
+    If x is already in a, insert it to the right of the rightmost x.
+
+    Optional args lo (default 0) and hi (default len(a)) bound the
+    slice of a to be searched.
+    """
+
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
+    if hi is None:
+        hi = len(a)
+    while lo < hi:
+        mid = (lo+hi)//2
+        if x < a[mid]: hi = mid
+        else: lo = mid+1
+    a.insert(lo, x)
+
+insort = insort_right   # backward compatibility
+
+def bisect_right(a, x, lo=0, hi=None):
+    """Return the index where to insert item x in list a, assuming a is sorted.
+
+    The return value i is such that all e in a[:i] have e <= x, and all e in
+    a[i:] have e > x.  So if x already appears in the list, a.insert(x) will
+    insert just after the rightmost x already there.
+
+    Optional args lo (default 0) and hi (default len(a)) bound the
+    slice of a to be searched.
+    """
+
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
+    if hi is None:
+        hi = len(a)
+    while lo < hi:
+        mid = (lo+hi)//2
+        if x < a[mid]: hi = mid
+        else: lo = mid+1
+    return lo
+
+bisect = bisect_right   # backward compatibility
+
+def insort_left(a, x, lo=0, hi=None):
+    """Insert item x in list a, and keep it sorted assuming a is sorted.
+
+    If x is already in a, insert it to the left of the leftmost x.
+
+    Optional args lo (default 0) and hi (default len(a)) bound the
+    slice of a to be searched.
+    """
+
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
+    if hi is None:
+        hi = len(a)
+    while lo < hi:
+        mid = (lo+hi)//2
+        if a[mid] < x: lo = mid+1
+        else: hi = mid
+    a.insert(lo, x)
+
+
+def bisect_left(a, x, lo=0, hi=None):
+    """Return the index where to insert item x in list a, assuming a is sorted.
+
+    The return value i is such that all e in a[:i] have e < x, and all e in
+    a[i:] have e >= x.  So if x already appears in the list, a.insert(x) will
+    insert just before the leftmost x already there.
+
+    Optional args lo (default 0) and hi (default len(a)) bound the
+    slice of a to be searched.
+    """
+
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
+    if hi is None:
+        hi = len(a)
+    while lo < hi:
+        mid = (lo+hi)//2
+        if a[mid] < x: lo = mid+1
+        else: hi = mid
+    return lo
+
+# Overwrite above definitions with a fast C implementation
+try:
+    from _bisect import *
+except ImportError:
+    pass