Add version info for os.kill and signal changes from #1220212.
diff --git a/Doc/library/signal.rst b/Doc/library/signal.rst
index 300c717..8ac7bee 100644
--- a/Doc/library/signal.rst
+++ b/Doc/library/signal.rst
@@ -78,16 +78,18 @@
 .. data:: CTRL_C_EVENT
 
    The signal corresponding to the CTRL+C keystroke event.
-
    Availability: Windows.
 
+   .. versionadded:: 2.7
+
 
 .. data:: CTRL_BREAK_EVENT
 
    The signal corresponding to the CTRL+BREAK keystroke event.
-
    Availability: Windows.
 
+   .. versionadded:: 2.7
+
 
 .. data:: NSIG