NetServices: Implement controls on the number of concurrent requests.

This change allows the user to control how many concurrent request can be done
per session. This is going to be helpful to running the tests as well; they were
all fired up in parallel, which sometimes leads to our test server refusing a
connection.

Change-Id: I4f1f40b28b8e0199ea5589b36cd8d00ecd849a63

docs/user/netservices/HttpSession.dox

@@ -219,6 +219,47 @@ namespace Network {
 */
 
 
+/*!
+	\fn void BHttpSession::SetMaxConnectionsPerHost(size_t maxConnections)
+	\brief Set the maximum number of connections per host.
+
+	A host is identified by the domain name and the port. You can limit the number of concurrent
+	connections to a host by tweaking this value.
+
+	The default value is 2 connections per host.
+
+	If the value is decreased, any requests that already started will not be affected. The new
+	value will only be applied when any new requests are added.
+
+	\param maxConnections The maximum number of connections per host. This value must between 1
+		and \c INT32_MAX.
+
+	\exception BRuntimeError In case the \a maxConnections is invalid.
+
+	\since Haiku R1
+*/
+
+
+/*!
+	\fn void BPrivate::Network::BHttpSession::SetMaxHosts(size_t maxConnections)
+	\brief Set the maximum number of concurrent hosts that can be connected to.
+
+	A host is identified by the domain name and the port. You can limit the number of concurrent
+	hosts by tweaking this value.
+
+	The default value is 10 concurrent hosts.
+
+	If the value is decreased, any requests that already started will not be affected. The new
+	value will only be applied when any new requests are added.
+
+	\param maxConnections The maximum number of hosts. The value must be at least 1.
+
+	\exception BRuntimeError In case the \a maxConnections is 0.
+
+	\since Haiku R1
+*/
+
+
 /*!
 	\var UrlEvent::HttpStatus
 	\brief The HTTP status code has been received, and can be accessed through the result object.