layout: restructure into src/ tests/ android/ scripts/ tools/

- extension/src/{port,platform,codepage} -> src/; native_render -> src/host
  (+ dxt, shaders/); libgr2 -> src/gr2; extension/third_party -> third_party
- extension/tests -> tests/port, libgr2/tests -> tests/gr2
- android-native -> android (build.sh, push-client.sh moved in)
- script -> scripts; tools/40250 -> tools/server; oracle -> tools/granny-oracle;
  perf tools -> tools/perf
- all build trees under build/ (native, release, android, port-gate)
- xrender:: CMake aliases -> mt::; port-map ledger impl paths rewritten

No code changes. ctest 15/15, port_gate macos+android PASS, port_map check 0 errors.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

third_party/cpython-2.7.18/Lib/importlib/__init__.py

@@ -0,0 +1,38 @@
+"""Backport of importlib.import_module from 3.x."""
+# While not critical (and in no way guaranteed!), it would be nice to keep this
+# code compatible with Python 2.3.
+import sys
+
+def _resolve_name(name, package, level):
+    """Return the absolute name of the module to be imported."""
+    if not hasattr(package, 'rindex'):
+        raise ValueError("'package' not set to a string")
+    dot = len(package)
+    for x in xrange(level, 1, -1):
+        try:
+            dot = package.rindex('.', 0, dot)
+        except ValueError:
+            raise ValueError("attempted relative import beyond top-level "
+                              "package")
+    return "%s.%s" % (package[:dot], name)
+
+
+def import_module(name, package=None):
+    """Import a module.
+
+    The 'package' argument is required when performing a relative import. It
+    specifies the package to use as the anchor point from which to resolve the
+    relative import to an absolute import.
+
+    """
+    if name.startswith('.'):
+        if not package:
+            raise TypeError("relative imports require the 'package' argument")
+        level = 0
+        for character in name:
+            if character != '.':
+                break
+            level += 1
+        name = _resolve_name(name[level:], package, level)
+    __import__(name)
+    return sys.modules[name]