Python 3 default args fix

Fix 0U and 0L as default args for Python 3 (tests committed in
previously commit of default_args.i).
Relates to issue #294.

Examples/test-suite/default_args.i

@@ -27,6 +27,12 @@
   void seek3(long offset = 0L) {}
   void seek4(unsigned long offset = 0UL) {}
   void seek5(unsigned long offset = 0U) {}
+  void seek6(unsigned long offset = 02U) {}
+  void seek7(unsigned long offset = 00U) {}
+  void seek8(unsigned long offset = 1U) {}
+  void seek9(long offset = 1L) {}
+  void seekA(long long offset = 1LL) {}
+  void seekB(unsigned long long offset = 1ULL) {}
 
   // Anonymous arguments
   int anonymous(int = 7771);

Source/Modules/python.cxx

@@ -1923,9 +1923,11 @@ public:
 	  // to be "0o" in Python 3 only (and as long as we still support Python
 	  // 2.5, this can't be done unconditionally).
 	  if (py3) {
-	    String *res = NewString("0o");
-	    Append(res, NewStringWithSize(s + 1, end - s - 1));
-	    return res;
+	    if (end - s > 1) {
+	      String *res = NewString("0o");
+	      Append(res, NewStringWithSize(s + 1, end - s - 1));
+	      return res;
+	    }
 	  }
 	}
       }