The change in flatten_http_headers to omit adding Host header wasbreaking

windows clients.
Instead, skip adding the host header when user has already specified one in the
boost asio based clients without modifying flatten_http_headers.

Author: kavyako

Release/include/cpprest/details/http_client_impl.h

@@ -57,10 +57,6 @@ static utility::string_t flatten_http_headers(const http_headers &headers)
     utility::string_t flattened_headers;
     for(auto iter = headers.begin(); iter != headers.end(); ++iter)
     {
-        utility::string_t header_name = iter->first;
-        if (utility::details::str_icmp(header_name, header_names::host)) {
-            continue;
-        }
         flattened_headers.append(iter->first);
         flattened_headers.push_back(':');
         flattened_headers.append(iter->second);

Release/src/http/client/http_client_asio.cpp

@@ -395,19 +395,17 @@ class asio_context : public request_context, public std::enable_shared_from_this
         request_stream.imbue(std::locale::classic());
 
         request_stream << method << " " << encoded_resource << " " << "HTTP/1.1" << CRLF;
-        request_stream << "Host: ";
 
         int port = base_uri.port();
         if (base_uri.is_port_default())
         {
             port = (m_connection->is_ssl() ? 443 : 80);
         }
 
-        std::string specified_host_header;
-        if (m_request.headers().match(header_names::host, specified_host_header)) {
-            request_stream << specified_host_header << CRLF;
-        } else {
-            request_stream << host << ":" << port << CRLF;
+        // Add the Host header if user has not specified it explicitly
+        if (!m_request.headers().has(header_names::host))
+        {
+            request_stream << "Host: " << host << ":" << port << CRLF;
         }
 
         // Extra request headers are constructed here.