Issue #12549: Correct test_platform to not fail when OS X returns 'x86_64'
as the processor type on some Mac systems.  Also fix NameError in fallback
_mac_ver_gestalt function.  And remove out-of-date URL in docs.
diff --git a/Lib/platform.py b/Lib/platform.py
index 6db7f19..710f21e 100755
--- a/Lib/platform.py
+++ b/Lib/platform.py
@@ -765,6 +765,7 @@
                    0x2: 'PowerPC',
                    0xa: 'i386'}.get(sysa,'')
 
+    versioninfo=('', '', '')
     return release,versioninfo,machine
 
 def _mac_ver_xml():