support finding packages in /usr/local, install to /usr/local by default

Patch: python-3.3.0b1-localpath.patch

Author: mcepl

Lib/site.py

@@ -75,7 +75,7 @@
 import _sitebuiltins
 
 # Prefixes for site-packages; add additional prefixes like /usr/local here
-PREFIXES = [sys.prefix, sys.exec_prefix]
+PREFIXES = [sys.prefix, sys.exec_prefix, '/usr/local']
 # Enable per user site-packages directory
 # set it to False to disable the feature or True to force the feature
 ENABLE_USER_SITE = None