Add a way for us to place jobs with a concurrency limit.

The main use case is having all threads stuck in ledgerData, fighting each other.

modules/ripple_core/functional/ripple_Job.cpp

@@ -7,17 +7,20 @@
 Job::Job ()
     : mType (jtINVALID)
     , mJobIndex (0)
+    , m_limit (0)
 {
 }
 
 Job::Job (JobType type, uint64 index)
     : mType (type)
     , mJobIndex (index)
+    , m_limit (0)
 {
 }
 
 Job::Job (JobType type,
           std::string const& name,
+          int limit,
           uint64 index,
           LoadMonitor& lm,
           FUNCTION_TYPE <void (Job&)> const& job)
@@ -25,6 +28,7 @@ Job::Job (JobType type,
     , mJobIndex (index)
     , mJob (job)
     , mName (name)
+    , m_limit(limit)
 {
     m_loadEvent = boost::make_shared <LoadEvent> (boost::ref (lm), name, false);
 }
@@ -52,6 +56,11 @@ void Job::rename (std::string const& newName)
     mName = newName;
 }
 
+int Job::getLimit () const
+{
+    return m_limit;
+}
+
 const char* Job::toString (JobType t)
 {
     switch (t)