Add default filters for sync types.

[jmalloc]

The default way that the RWLock and Once are rendered does not offer much useful information. For example:

    once:             {
        done: 0
        m:    {
            state: 0
            sema:  0
        }
    }
    m:                {
        w:           {
            state: 0
            sema:  0
        }
        writerSem:   0
        readerSem:   0
        readerCount: 0
        readerWait:  0
    }

An improvement would be to simply render the types, or if possible showing the locked state (for locks) or done state (for once) in a more friendly manner.