use gcd to read child data and monitor if child is still alive.

git-svn-id: svn://qnap.local/TwoTerm/branches/gcd_dispatch@3105 5590a31f-7b70-45f8-8c82-aa3a8e5f4507

TermWindowController.h

@@ -30,6 +30,12 @@
     
     int _child;
     
+    int _fd;
+    pid_t _pid;
+    
+    dispatch_source_t _read_source;
+    dispatch_source_t _wait_source;
+    
 }
 
 @property (nonatomic, retain) NSDictionary *parameters;