Build fix for Visual Studio 2015

Author: Robert Hegner

boost/network/protocol/http/client/connection/async_protocol_handler.hpp

@@ -262,7 +262,7 @@ struct http_async_protocol_handler {
     typename headers_range<basic_response<Tag> >::type transfer_encoding_range =
         headers.equal_range("Transfer-Encoding");
     is_chunk_encoding =
-        !empty(transfer_encoding_range) &&
+        !boost::empty(transfer_encoding_range) &&
         boost::iequals(boost::begin(transfer_encoding_range)->second,
                        "chunked");
     headers_promise.set_value(headers);

boost/network/protocol/http/client/connection/sync_base.hpp

@@ -133,10 +133,10 @@ struct sync_connection_base_impl {
     // look for the content-length header
     typename headers_range<basic_response<Tag> >::type content_length_range =
         headers(response_)["Content-Length"];
-    if (empty(content_length_range)) {
+    if (boost::empty(content_length_range)) {
       typename headers_range<basic_response<Tag> >::type
           transfer_encoding_range = headers(response_)["Transfer-Encoding"];
-      if (empty(transfer_encoding_range)) {
+      if (boost::empty(transfer_encoding_range)) {
         read_body_normal(socket_, response_, response_buffer, body_stream);
         return;
       }

boost/network/protocol/http/client/connection/sync_normal.hpp

@@ -95,7 +95,7 @@ struct http_sync_connection
     connection_base::read_body(socket_, response_, response_buffer);
     typename headers_range<basic_response<Tag> >::type connection_range =
         headers(response_)["Connection"];
-    if (version_major == 1 && version_minor == 1 && !empty(connection_range) &&
+    if (version_major == 1 && version_minor == 1 && !boost::empty(connection_range) &&
         boost::iequals(boost::begin(connection_range)->second, "close")) {
       close_socket();
     } else if (version_major == 1 && version_minor == 0) {

boost/network/protocol/http/client/connection/sync_ssl.hpp

@@ -142,7 +142,7 @@ struct https_sync_connection
     connection_base::read_body(socket_, response_, response_buffer);
     typename headers_range<basic_response<Tag> >::type connection_range =
         headers(response_)["Connection"];
-    if (version_major == 1 && version_minor == 1 && !empty(connection_range) &&
+    if (version_major == 1 && version_minor == 1 && !boost::empty(connection_range) &&
         boost::iequals(boost::begin(connection_range)->second, "close")) {
       close_socket();
     } else if (version_major == 1 && version_minor == 0) {

boost/network/protocol/http/policies/pooled_connection.hpp

@@ -135,7 +135,7 @@ struct pooled_connection_policy : resolver_policy<Tag>::type {
         typename headers_range<basic_response<Tag> >::type connection_range =
             headers(response_)["Connection"];
         if (version_major == 1 && version_minor == 1 &&
-            !empty(connection_range) &&
+            !boost::empty(connection_range) &&
             boost::begin(connection_range)->second == string_type("close")) {
           pimpl->close_socket();
         } else if (version_major == 1 && version_minor == 0) {