Support string width in syslog_printf, like %5s
Support string width in syslog_printf, like %5s

TJ-Hidetaka-Takano/mrubyc,mrubyc/mrubyc,TJ-Hidetaka-Takano/mrubyc,mrubyc/mrubyc,TJ-Hidetaka-Takano/mrubyc,TJ-Hidetaka-Takano/mrubyc