pcp

Logger PMDA can now handle multiple clients.

• src/pmdas/logger/event.c (ctx_start_callback): New function. (ctx_end_callback): Ditto. (event_init): Register callbacks. (event_fetch): Call event_create to get new data.
• src/pmdas/logger/event.h: Removed event_create() prototype.
• src/pmdas/logger/logger.c (logger_end_contextCallBack): No longer call event_cleanup(), which is now called in ctx_end_callback().
• src/pmdas/logger/logger.h: Added get_monitor_fd() prototype.
• src/pmdas/logger/loggerMain.c (get_monitor_fd): New function. (loggerMain): Open the logfile with O_NONBLOCK. Let event_fetch() call event_create().
• src/pmdas/logger/percontext.h: Update comment.