libdebugger/powerpc: Add PowerPC support

Closes #5098

cpukit/libdebugger/rtems-debugger-server.c

@@ -1797,7 +1797,16 @@ rtems_debugger_session(void)
 
   if (rtems_debugger_server_flag(RTEMS_DEBUGGER_FLAG_RESET)) {
     rtems_debugger_printf("rtems-db: shutdown\n");
+    /*
+     * Wait a moment to let any disconnection protocol a transport has
+     * complete. The legacy stack needs this to close the connection
+     * to GDB and clean up.
+     */
     sleep(2);
+    /*
+     * No special exit code, the user will asked GDB to kill the
+     * target
+     */
     rtems_fatal_error_occurred(1122);
   }
 

cpukit/libdebugger/rtems-debugger-target.h

@@ -92,9 +92,11 @@ typedef struct rtems_debugger_target_swbreak {
 } rtems_debugger_target_swbreak;
 
 /**
- * Target memory update handler. If set this is called to modify
- * the executable memory. It may not be possible to make it
- * read/write.
+ * Target executable memory update handler. If set the handler is
+ * called to modify the executable memory. The target's executable
+ * memory may not be directly writable. The handler is responsible for
+ * making sure the code update is ready to be executed, for example
+ * caches are flushed.
  */
 typedef int (*rtems_debugger_target_code_writer)(void*       address,
                                                  const void* data,