More cleanup, based around searches for "Google.ProtocolBuffers"

- Remove some old proto2-based C#-only messages
- Remove the "build" directory which only contained out-of-date files
- Remove the csharp_namespace option from proto2 messages
- Change "Google.ProtocolBuffers" to "Google.Protobuf" in other messages

1 files changed, 1 insertions, 1 deletions

diff --git a/src/google/protobuf/field_mask.proto b/src/google/protobuf/field_mask.proto
index 35b1acc3..ad7a1dfa 100644
--- a/src/google/protobuf/field_mask.proto
+++ b/src/google/protobuf/field_mask.proto
@@ -34,7 +34,7 @@ package google.protobuf;
 option java_multiple_files = true;
 option java_outer_classname = "FieldMaskProto";
 option java_package = "com.google.protobuf";
-option csharp_namespace = "Google.ProtocolBuffers";
+option csharp_namespace = "Google.Protobuf";
 option objc_class_prefix = "GPB";