core: slim down `common.hpp`

Change-Id: I875c35147edd2261fbaa24e809c170d5cd9b94d3
diff --git a/daemon/face/ethernet-transport.cpp b/daemon/face/ethernet-transport.cpp
index 43f7e91..9ddbdb7 100644
--- a/daemon/face/ethernet-transport.cpp
+++ b/daemon/face/ethernet-transport.cpp
@@ -133,8 +133,8 @@
   if (sent < 0)
     handleError("Send operation failed: " + m_pcap.getLastError());
   else if (static_cast<size_t>(sent) < buffer.size())
-    handleError("Failed to send the full frame: size=" + to_string(buffer.size()) +
-                " sent=" + to_string(sent));
+    handleError("Failed to send the full frame: size=" + std::to_string(buffer.size()) +
+                " sent=" + std::to_string(sent));
   else
     // print block size because we don't want to count the padding in buffer
     NFD_LOG_FACE_TRACE("Successfully sent: " << block.size() << " bytes");