Merge commit '36bca61764984ff5395653cf8377ec5daa71b709' as 'libs/protobuf'

libs/protobuf/csharp/protos/unittest_issue6936_a.proto

@@ -0,0 +1,15 @@
+syntax = "proto3";
+
+package unittest_issues;
+
+option csharp_namespace = "UnitTest.Issues.TestProtos";
+
+// This file is used as part of a unit test for issue 6936
+// We don't need to use it, we just have to import it in both 
+// "extensions_issue6936_b.proto" and "extensions_issue6936_c.proto"
+
+import "google/protobuf/descriptor.proto";
+
+extend google.protobuf.MessageOptions {
+    string opt = 50000;
+}