[pgpool-hackers: 3447] Change difinition of vsyslog to syslog

[Takuma Hoshiai]

Hi, 

The configure.ac contain to check vsyslog(). And check to exist difinition of HAVE_VSYSLOG if pgpool's log outputs to syslog.
But, currently it didn't use vsyslog(), use syslog(). 

I want to fix vsyslog() to syslog() in configure and some difinitions.

This fix found by the following:
https://www.pgpool.net/mantisbt/view.php?id=548

If you have any thoughts on that please share it with me.

-- 
Takuma Hoshiai <hoshiai at sraoss.co.jp>