Fixed octave version check and enabled VPATH build for check-octave-operator example

Examples/octave/operator/runme.m

@@ -3,6 +3,9 @@ if exist("crash_dumps_octave_core", "builtin")
   crash_dumps_octave_core(0);
 endif
 
+scriptDir = fileparts(mfilename('fullpath'));
+addpath(scriptDir);
+
 # Operator overloading example
 swigexample
 

Lib/octave/octrun.swg

@@ -812,7 +812,7 @@ SWIGRUNTIME void swig_acquire_ownership_obj(void *vptr, int own);
       return as_value();
     }
 
-#if SWIG_OCTAVE_PREREQ(6,0,0)
+#if SWIG_OCTAVE_PREREQ(4,4,0)
     virtual bool isobject() const {
 #else
     virtual bool is_object() const {