[sheepdog] rename printf functions

[MORITA Kazutaka]

Hi all,

1. How about introducing the following functions?

   sd_emerg()  to log message with log level SDOG_EMERG
   sd_alert()  to log message with log level SDOG_ALERT
   sd_crit()   to log message with log level SDOG_CRIT
   sd_err()    to log message with log level SDOG_ERR
               (sd_eprintf will be removed)
   sd_warn()   to log message with log level SDOG_WARN
   sd_notice() to log message with log level SDOG_NOTICE
   sd_info()   to log message with log level SDOG_INFO
               (sd_iprintf will be removed)
   sd_debug()  to log message with log level SDOG_DEBUG
               (sd_dprintf will be removed)

2. How about using sd_eprintf (or sd_err) instead of fprintf(stderr)?

   The output won't change even in collie because the result of
   sd_eprintf is same as fprintf(stderr) when logger is not
   initialized.


Thanks,

Kazutaka