bpo-1529353: IDLE: squeeze large output in the shell (GH-7626)

(cherry picked from commit 604e7b9931f9e7881a2941816e538f5f15930db8)

Co-authored-by: Tal Einat <taleinat+github@gmail.com>
diff --git a/Lib/idlelib/pyshell.py b/Lib/idlelib/pyshell.py
index 52c11e3..5458c59 100755
--- a/Lib/idlelib/pyshell.py
+++ b/Lib/idlelib/pyshell.py
@@ -856,6 +856,10 @@
         ("help", "_Help"),
     ]
 
+    # Extend right-click context menu
+    rmenu_specs = OutputWindow.rmenu_specs + [
+        ("Squeeze", "<<squeeze-current-text>>"),
+    ]
 
     # New classes
     from idlelib.history import History