MXS-1835 Turn all protocol modules into C++

server/modules/protocol/CDC/CMakeLists.txt

@@ -1,4 +1,4 @@
-add_library(cdc SHARED cdc.c)
+add_library(cdc SHARED cdc.cc)
 target_link_libraries(cdc maxscale-common)
 set_target_properties(cdc PROPERTIES VERSION "1.0.1")
 install_module(cdc core)

server/modules/protocol/CDC/cdc.cc

@@ -59,9 +59,11 @@ static void write_auth_err(DCB *dcb);
 
 static char* cdc_default_auth()
 {
-    return "CDCPlainAuth";
+    return const_cast<char*>("CDCPlainAuth");
 }
 
+extern "C"
+{
 /**
  * The module entry point routine. It is this routine that
  * must populate the structure that is referred to as the
@@ -111,6 +113,8 @@ MXS_MODULE* MXS_CREATE_MODULE()
     return &info;
 }
 
+}
+
 /**
  * Read event for EPOLLIN on the CDC protocol module.
  *