Feature: add pgpool_adm_pcp_proc_info.

Feature: add pgpool_adm_pcp_proc_info.

This commit adds new pgpool_adm extension function:
pcp_proc_info. Also add new fields: client_host, client_port and SQL
statement to pcp_proc_info and "show pool_pools". With these additions
now it is possible to track the relationship among clients of pgpool,
pgpool itself and PostgreSQL.

Moreover the commit allows to know what commands (statements) are last
executed by using pcp_proc_info. Previously it was not possible unless
looking into the pgpool log.

lipcp.so version is bumped from 2.0 to 2.1.