rename Greenlet.link()'s argument to 'callback'

Previously it was called 'receiver'. Also link_exception() had
a default value for it which was None, but it did not work,
since linking to current greenlet feature was removed some time ago.

Section on spawn_link was removed from doc since these functions have
been gone for some time as well.

Closes #244.

doc/gevent.rst

@@ -38,9 +38,9 @@ It also a good idea to override :meth:`__str__`: if :meth:`_run` raises an excep
 .. automethod:: Greenlet.join
 .. automethod:: Greenlet.get
 .. automethod:: Greenlet.kill(exception=GreenletExit, block=False, timeout=None)
-.. automethod:: Greenlet.link(receiver=None)
-.. automethod:: Greenlet.link_value(receiver=None)
-.. automethod:: Greenlet.link_exception(receiver=None)
+.. automethod:: Greenlet.link(callback)
+.. automethod:: Greenlet.link_value(callback)
+.. automethod:: Greenlet.link_exception(callback)
 .. automethod:: Greenlet.unlink
 
 
@@ -79,21 +79,6 @@ Spawn helpers
     As this returns a raw greenlet, it does not have all the useful methods that
     :class:`gevent.Greenlet` has and should only be used as an optimization.
 
-.. function:: spawn_link(function, *args, **kwargs)
-              spawn_link_value(function, *args, **kwargs)
-              spawn_link_exception(function, *args, **kwargs)
-
-    This are the shortcuts for::
-
-        g = spawn(function, *args, **kwargs)
-        g.link() # or g.link_value() or g.link_exception()
-
-    As :meth:`Greenlet.link` without argument links to the current greenlet, a :class:`gevent.greenlet.LinkedExited`
-    exception will be raised if the newly spawned greenlet exits. It is not meant as a way of inter-greenlet communication
-    but more of a way to assert that a background greenlet is running at least as long as the current greenlet.
-
-    See :meth:`Greenlet.link`, :meth:`Greenlet.link_value` and :meth:`Greenlet.link_exception` for details.
-
 
 Useful general functions
 ------------------------

gevent/greenlet.py

@@ -346,28 +346,28 @@ class Greenlet(greenlet):
         if self.ready() and self._links and not self._notifier:
             self._notifier = self.parent.loop.run_callback(self._notify_links)
 
-    def link(self, receiver, SpawnedLink=SpawnedLink):
+    def link(self, callback, SpawnedLink=SpawnedLink):
         """Link greenlet's completion to a callable.
 
-        The *receiver* will be called with this instance as an argument
+        The *callback* will be called with this instance as an argument
         once this greenlet's dead. A callable is called in its own greenlet.
         """
-        self.rawlink(SpawnedLink(receiver))
+        self.rawlink(SpawnedLink(callback))
 
-    def unlink(self, receiver):
-        """Remove the receiver set by :meth:`link` or :meth:`rawlink`"""
+    def unlink(self, callback):
+        """Remove the callback set by :meth:`link` or :meth:`rawlink`"""
         try:
-            self._links.remove(receiver)
+            self._links.remove(callback)
         except ValueError:
             pass
 
-    def link_value(self, receiver, SpawnedLink=SuccessSpawnedLink):
-        """Like :meth:`link` but *receiver* is only notified when the greenlet has completed successfully"""
-        self.link(receiver=receiver, SpawnedLink=SpawnedLink)
+    def link_value(self, callback, SpawnedLink=SuccessSpawnedLink):
+        """Like :meth:`link` but *callback* is only notified when the greenlet has completed successfully"""
+        self.link(callback, SpawnedLink=SpawnedLink)
 
-    def link_exception(self, receiver=None, SpawnedLink=FailureSpawnedLink):
-        """Like :meth:`link` but *receiver* is only notified when the greenlet dies because of unhandled exception"""
-        self.link(receiver=receiver, SpawnedLink=SpawnedLink)
+    def link_exception(self, callback, SpawnedLink=FailureSpawnedLink):
+        """Like :meth:`link` but *callback* is only notified when the greenlet dies because of unhandled exception"""
+        self.link(callback, SpawnedLink=SpawnedLink)
 
     def _notify_links(self):
         while self._links: