Expand the deprecation warning for get_transaction() to cover

the most common cases (commit() and abort()) -- it's not really
obvious that shortcut spelling exist for those.

src/transaction/__init__.py

@@ -35,5 +35,7 @@ def abort(sub=False):
 
 def get_transaction():
     from ZODB.utils import deprecated36
-    deprecated36("   use transaction.get() instead of get_transaction()")
+    deprecated36("""   use transaction.get() instead of get_transaction().
+   transaction.commit() is a shortcut spelling of transaction.get().commit(),
+   and transaction.abort() of transaction.get().abort().""")
     return get()