Compat w/ git < 1.8.
Ignore generated test scaffolding files.
Exclude Python build artifacts.
Merge remote-tracking branch 'upstream/master'
Fix 'error: a class-key must be used when declaring a friend' compile error.
Fix testcase compile failure under gcc 4.6:

google/protobuf/map_test.cc:88:16: error: expected ‘;’ at end of member declaration
google/protobuf/map_test.cc:88:18: error: ‘override’ does not name a type
.
Merge pull request #88 from tseaver/fix-class_key_must_be_declared_w_friend

Fix compiler error: "a class-key must be used when declaring a friend"