Modify pgpool-II version values to current newest ones

Actually, every time when making a new pgpool-installer, the version
values should be adjusted to designated version.
Replace the installing package for backend nodes

A new extensions RPM, which separated installing process of the pgpool-II
functions from main RPM, is added.
Merge pull request #2 from yuta-masano/update_for_3.3.4

Update for 3.3.4