Plugin: add export to buffer_size function.
Plugin: add export to buffer_size function.

 This patch fixes a problem where `mk_plugin_load_symbol` returns 0
 for `_mkp_network_io_buffer_size` function.

sbagmeijer/monkey,dougsko/monkey,sujayraaj/monkeyTest,WilliamRen/monkey-1,dougsko/monkey,sujayraaj/monkeyTest,dougsko/monkey,sbagmeijer/monkey,dougsko/monkey,sujayraaj/monkeyTest,sujayraaj/monkey_rtems,WilliamRen/monkey-1,monkey/monkey,sbagmeijer/monkey,sujayraaj/monkey,sujayraaj/monkey,sujayraaj/monkey_rtems,dougsko/monkey,sbagmeijer/monkey,dreamsxin/monkey,dreamsxin/monkey,WilliamRen/monkey-1,dreamsxin/monkey,monkey/monkey,monkey/monkey,dreamsxin/monkey,sujayraaj/monkey_rtems,sujayraaj/monkey,WilliamRen/monkey-1,monkey/monkey,sbagmeijer/monkey,sujayraaj/monkey,monkey/monkey,sujayraaj/monkey,sujayraaj/monkey_rtems,sujayraaj/monkeyTest,dreamsxin/monkey,WilliamRen/monkey-1,sujayraaj/monkey_rtems,monkey/monkey