base: changes for GDB monitor

- add a new function 'binary_ready_hook_for_gdb()' in ldso. GDB can set a
  breakpoint at this function to know when ldso has loaded the binary
  into memory.
- get the thread state from the NOVA kernel immediately on 'pause()'

Fixes #1968

repos/base-nova/include/nova/native_thread.h

@@ -31,6 +31,7 @@ struct Genode::Native_thread
 	addr_t ec_sel;     /* selector for execution context */
 	addr_t exc_pt_sel; /* base of event portal window */
 	bool   vcpu;       /* true if thread is a virtual CPU */
+	addr_t initial_ip; /* initial IP of local thread */
 
 	/* receive window for capability selectors received at the server side */
 	Receive_window rcv_window;
@@ -38,7 +39,9 @@ struct Genode::Native_thread
 	Native_capability pager_cap;
 
 	Native_thread() : ec_sel(INVALID_INDEX),
-	                  exc_pt_sel(INVALID_INDEX), vcpu(false) { }
+	                  exc_pt_sel(INVALID_INDEX),
+	                  vcpu(false),
+	                  initial_ip(0) { }
 };
 
 #endif /* _INCLUDE__NOVA__NATIVE_THREAD_H_ */