SF patch #1438387, PEP 328: relative and absolute imports.

- IMPORT_NAME takes an extra argument from the stack: the relativeness of
   the import. Only passed to __import__ when it's not -1.

 - __import__() takes an optional 5th argument for the same thing; it
   __defaults to -1 (old semantics: try relative, then absolute)

 - 'from . import name' imports name (be it module or regular attribute)
   from the current module's *package*. Likewise, 'from .module import name'
   will import name from a sibling to the current module.

 - Importing from outside a package is not allowed; 'from . import sys' in a
   toplevel module will not work, nor will 'from .. import sys' in a
   (single-level) package.

 - 'from __future__ import absolute_import' will turn on the new semantics
   for import and from-import: imports will be absolute, except for
   from-import with dots.

Includes tests for regular imports and importhooks, parser changes and a
NEWS item, but no compiler-package changes or documentation changes.

Include/import.h

@@ -14,8 +14,16 @@ PyAPI_FUNC(PyObject *) PyImport_ExecCodeModuleEx(
 PyAPI_FUNC(PyObject *) PyImport_GetModuleDict(void);
 PyAPI_FUNC(PyObject *) PyImport_AddModule(const char *name);
 PyAPI_FUNC(PyObject *) PyImport_ImportModule(const char *name);
+PyAPI_FUNC(PyObject *) PyImport_ImportModuleLevel(char *name,
+	PyObject *globals, PyObject *locals, PyObject *fromlist, int level);
+
+/* For DLL compatibility */
+#undef PyImport_ImportModuleEx
 PyAPI_FUNC(PyObject *) PyImport_ImportModuleEx(
 	char *name, PyObject *globals, PyObject *locals, PyObject *fromlist);
+#define PyImport_ImportModuleEx(n, g, l, f) \
+	PyImport_ImportModuleLevel(n, g, l, f, -1);
+
 PyAPI_FUNC(PyObject *) PyImport_Import(PyObject *name);
 PyAPI_FUNC(PyObject *) PyImport_ReloadModule(PyObject *m);
 PyAPI_FUNC(void) PyImport_Cleanup(void);