thread_sync.c: Update rdoc for Queue [skip ci]

* thread_sync.c: [DOC] Update documentation for Queue class
  description.  [Fix GH-1292]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54146 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Thu Mar 17 17:20:28 2016  Anton Davydov  <antondavydov.o@gmail.com>
+
+	* thread_sync.c: [DOC] Update documentation for Queue class
+	  description.  [Fix GH-1292]
+
 Thu Mar 17 17:14:51 2016  Dinar Valeev  <dvaleev@suse.com>
 
 	* gc.c (tick): Use __builtin_ppc_get_timebase for POWER arch.

thread_sync.c

@@ -632,7 +632,13 @@ queue_do_close(VALUE self, int is_szq)
 /*
  *  Document-class: Queue
  *
- *  This class provides a way to synchronize communication between threads.
+ *  The Queue class implements multi-producer, multi-consumer queues.
+ *  It is especially useful in threaded programming when information
+ *  must be exchanged safely between multiple threads. The Queue class
+ *  implements all the required locking semantics.
+ *
+ *  The class implements FIFO type of queue. In a FIFO queue, the first
+ *  tasks added are the first retrieved.
  *
  *  Example:
  *