MINOR: listener: implement GUID support

MINOR: listener: implement GUID support

This commit is similar with the two previous ones. Its purpose is to add
GUID support on listeners. Due to bind_conf and listeners configuration,
some specifities were required.

Its possible to define several listeners on a single bind line, for
example by specifying multiple addresses. As such, it's impossible to
support a "guid" keyword on a bind line. The problem is exacerbated by
the cloning of listeners when sharding is used.

To resolve this, a new keyword "guid-prefix" is defined for bind lines.
It allows to specify a string which will be used as a prefix for
automatically generated GUID for each listeners attached to a bind_conf.

Automatic GUID listeners generation is implemented via a new function
bind_generate_guid(). It is called on post-parsing, after
bind_complete_thread_setup(). For each listeners on a bind_conf, a new
GUID is generated with bind_conf prefix and the index of the listener
relative to other listeners in the bind_conf. This last value is stored
in a new bind_conf field named <guid_idx>. If a GUID cannot be inserted,
for example due to a non-unique value, an error is returned, startup is
interrupted with configuration rejected.