Make 'active_seeds' and 'active_downloads' use -1 as unlimited

docs/manual.rst

@@ -3026,7 +3026,7 @@ the *QBone scavenger service*. For more details, see QBSS_.
 downloading torrents the queuing mechanism allows. The target number of active
 torrents is ``max(active_downloads, active_seeds)``. ``active_downloads`` and
 ``active_seeds`` are upper limits on the number of downloading torrents and
-seeding torrents respectively.
+seeding torrents respectively. Setting the value to -1 will mean unlimited.
 
 For example if there are 10 seeding torrents and 10 downloading torrents, and
 ``active_downloads`` is 4 and ``active_seeds`` is 4, there will be no seed

src/session_impl.cpp

@@ -1308,6 +1308,11 @@ namespace aux {
 		int num_downloaders = settings().active_downloads;
 		int num_seeds = settings().active_seeds;
 
+        if (num_downloaders == -1)
+            num_downloaders = (std::numeric_limits<int>::max)();
+        if (num_seeds == -1)
+            num_seeds = (std::numeric_limits<int>::max)();
+            
 		for (torrent_map::iterator i = m_torrents.begin()
 			, end(m_torrents.end()); i != end; ++i)
 		{