First (uncontroversial) part of issue 9807.

* Expose the build flags to Python as sys.abiflags
* Shared library libpythonX.Y<abiflags>.so
* python-config --abiflags
* Make two distutils tests that failed with --enable-shared (even before this
  patch) succeed.
* Fix a few small style issues.

Python/sysmodule.c

@@ -1520,6 +1520,10 @@ _PySys_Init(void)
                         PyLong_FromVoidPtr(PyWin_DLLhModule));
     SET_SYS_FROM_STRING("winver",
                         PyUnicode_FromString(PyWin_DLLVersionString));
+#endif
+#ifdef ABIFLAGS
+    SET_SYS_FROM_STRING("abiflags",
+                        PyUnicode_FromString(ABIFLAGS));
 #endif
     if (warnoptions == NULL) {
         warnoptions = PyList_New(0);