Add openssl support
Allow to specify PostgreSQL library directory.

By using "PGLIB" environment variable, pgpool_setup sets
LD_LIBRARY_PATH.
Adopt PostgreSQL 9.4 having to_regclass.

PostgreSQL 9.4 has built-in function "to_regclass", which has
equivalent functionality of pgpool_regclass. Now pgpool searches
to_regclass first then try pgpool_regclass.
Fix unportable code related to SO_REUSEPORT.

There are several places using setsockopt(sock, SOL_SOCKET,
SO_REUSEPORT...). SO_REUSEPORT is not available on all Linux kernels
and the source code uses ifdef to detect the feature in the compile
time. Problem is, the binary created with kernel which provides the
feature cannot run on a kernel which does not provide the feature. Fix
is, detecting the feature in the run time by checking error code
returned by setsockopt() and ignore it if the cause of the error is
lacking the feature.
Adopt PostgreSQL 9.4 having to_regclass.

PostgreSQL 9.4 has built-in function "to_regclass", which has
equivalent functionality of pgpool_regclass. Now pgpool searches
to_regclass first then try pgpool_regclass.
Use 3.3-stable tree head.