Fixing a bug where the cached doxygen docstring could be deleted while still in use, causing swig to segfault

CHANGES.current

@@ -18,6 +18,9 @@ Version 4.0.0 (in progress)
             Only show a single documentation entry for functions with default arguments when
             using autodoc.
 
+            Fixed a bug where a cached doxygen docstring could be deleted while still in use,
+            causing swig to segfault.
+
 2019-01-22: vadz
             [Ruby, Octave] #1424 Improve autodoc parameter naming.
 

Source/Modules/python.cxx

@@ -1571,6 +1571,11 @@ public:
 	  // depends on the comment which is not going to change, so we can
 	  // safely cache it.
 	  Setattr(n, "python:docstring", Copy(docstr));
+	} else {
+	  // Must copy here since if the docstring is multi-line, the String*
+	  // here will get Deleted below, which is bad if it is a pointer to
+	  // the cached object!
+	  docstr = Copy(docstr);
 	}
       }
     }