First cut of database_redirect_preference_list and app_name_redirect_preference_list implementation.

These allow more fine control of load balancing by specifying database
name or application name. See [pgpool-hackers: 589] for more details.
while looking at the coverity issue "1222989 Bad bit shift operation" and
"1222990 Bad bit shift operation", it has come to light that set_fd(..),
and isset_fd(..) function implementation are faulty and on top of that
for some unknown reason, these functions are trying to reinvent the wheel
by not using the standard API (fd_set) already exists for same purpose.
So this commit removes the isset_fd() and set_fd() functions and adopts
the more sane choice of using FD_SET and FD_ISSET functions.
Add new parameter "allow_sql_comments".

SQL comments (/* ... */) effectively prevent load balancing and query
cache because pgpool-II strictly checks if the query starts with
"SELECT...". The new parameter removes the restriction and allows to
use SQL comments without disturbing load balancing and query
cache. For backward compatibility sake, the default is off.
Fix test 0007 to use $PSQL etc rather than bare command names.
Support IPv6 connections to PostgreSQL.

Now pgpool-II accepts IPv6 address in backend_hostname* such as '::1'.
Note that pgpool-II still does not bind to IPv6 address however.

Patch contributed by Michael Stapelberg.
Fix coverity issues 1233455, 1233456, 1233457 for regex_array.c.
Allow pgpool-II bind to IPv6 address.

Note that pcp still binds to IPv4 and UNIX domain socket.

Patch contributed by Michael Stapelberg.
fixing the expected output of watchdog regression test, which is failing because
of watchdog escalation log message changed by exception manager import patch.
fixing small coverity issues: 751966 Argument cannot be negative,
1111399 Explicit null dereferenced and 1111488 Uninitialized scalar variable
Add release notes
Fix typos
Explicitly stats that the number of slaves is not necessarily 1.
Final checkin of series for fixing "[pgpool-hackers: 592]. pool_error and elog",
This commit removes all occurrences of pool_error() and replace those with ereport().
The checking also integrates the exception manager to watchdog code, which was the last
remaining TODO of importing the exception and memory managers to pgpool-II
Fix typo in an error message.

Per Scalia, John.
Fix add_regex_array.

It addresses out of the array range if empty string is given.
Also use pre computed string length to save a few cycle.
Fix typo in an error message.
Fix typo in docs.

Per Yaron Naveh.