Fixes issue 3031: DCC plugin CPU/memory usage issues

Change-Id: I16eb04146240db986ead58669676fbf66c7fab9b
Reviewed-on: http://gerrit.dmdirc.com/745
Reviewed-by: Chris Smith <chris@dmdirc.com>
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>

src/com/dmdirc/addons/dcc/DCC.java

@@ -197,6 +197,7 @@ public abstract class DCC implements Runnable {
 
             // Sleep for a short period of time to reduce CPU usage.
             try {
+                Thread.yield();
                 Thread.sleep(100);
             } catch (InterruptedException ie) {
             }