This module, a standalone version of MCE::Mutex, implements locking methods
that can be used to coordinate access to shared data from multiple workers
spawned as processes or threads.

The inspiration for this module came from reading Mutex for Ruby.

$m1 = Mutex->new( );
$m1->impl();   # Channel
$m2 = Mutex->new( path => /tmp/my.lock );
$m2->impl();   # Flock
$m3 = Mutex->new( impl => "Channel" );
$m3->impl();   # Channel
$m4 = Mutex->new( impl => "Flock" );
$m4->impl();   # Flock