Add an accessor function to set srv_io_thread_op_info, change the type to const char*, also change the type of srv_io_thread_function to const char*


innobase/srv/srv0srv.c:
  Add an accessor function to set srv_io_thread_op_info, change the type to const char*, also change the type of srv_io_thread_function to const char*
innobase/include/srv0srv.h:
  Add an accessor function to set srv_io_thread_op_info, change the type to const char*, also change the type of srv_io_thread_function to const char*
innobase/os/os0file.c:
  Add an accessor function to set srv_io_thread_op_info, change the type to const char*, also change the type of srv_io_thread_function to const char*
innobase/fil/fil0fil.c:
  Add an accessor function to set srv_io_thread_op_info, change the type to const char*, also change the type of srv_io_thread_function to const char*