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.
diff --git a/Misc/python-config.in b/Misc/python-config.in
index 31df527..ba9183e 100644
--- a/Misc/python-config.in
+++ b/Misc/python-config.in
@@ -6,7 +6,7 @@
 import sysconfig
 
 valid_opts = ['prefix', 'exec-prefix', 'includes', 'libs', 'cflags',
-              'ldflags', 'extension-suffix', 'help']
+              'ldflags', 'extension-suffix', 'help', 'abiflags']
 
 def exit_with_usage(code=1):
     print("Usage: {0} [{1}]".format(
@@ -56,3 +56,6 @@
 
     elif opt == '--extension-suffix':
         print(sysconfig.get_config_var('SO'))
+
+    elif opt == '--abiflags':
+        print(sys.abiflags)