Changes for C to C++. Adding extern C to header files for compatibility.
diff --git a/config.w32 b/config.w32
index 5347bae..7247cfa 100644
--- a/config.w32
+++ b/config.w32
@@ -322,7 +322,7 @@
     "src\\core\\ext\\filters\\message_size\\message_size_filter.c " +
     "src\\core\\ext\\filters\\workarounds\\workaround_cronet_compression_filter.c " +
     "src\\core\\ext\\filters\\workarounds\\workaround_utils.c " +
-    "src\\core\\plugin_registry\\grpc_plugin_registry.c " +
+    "src\\core\\plugin_registry\\grpc_plugin_registry.cc " +
     "src\\boringssl\\err_data.c " +
     "third_party\\boringssl\\crypto\\aes\\aes.c " +
     "third_party\\boringssl\\crypto\\aes\\key_wrap.c " +