Fix several clazy issue:

* Suppress non-POD static [-Wclazy-non-pod-global-static]
* Call to temporary is a no-op: [-Wclazy-writing-to-temporary]
* Unused QString [-Wclazy-unused-non-trivial-variable]

src/App/DocumentPyImp.cpp

@@ -275,7 +275,9 @@ PyObject*  DocumentPy::addObject(PyObject *args, PyObject *kwd)
             if (pyvp.hasAttr("__vobject__")) {
                 pyvp.setAttr("__vobject__", pyftr.getAttr("ViewObject"));
             }
-            pyftr.getAttr("ViewObject").setAttr("Proxy", pyvp);
+
+            Py::Object pyprx(pyftr.getAttr("ViewObject"));
+            pyprx.setAttr("Proxy", pyvp);
             return Py::new_reference_to(pyftr);
         }
         catch (Py::Exception& e) {

src/App/PropertyLinks.cpp

@@ -2813,7 +2813,6 @@ public:
             tmp.swap(links);
             for(auto link : tmp) {
                 auto owner = static_cast<DocumentObject*>(link->getContainer());
-                QString path = QString::fromUtf8(link->filePath.c_str());
                 // adjust file path for each PropertyXLink
                 DocInfo::get(filename,owner->getDocument(),link,link->objectName.c_str());
             }

src/Base/Base64.cpp

@@ -32,7 +32,7 @@
 
 #include "Base64.h"
 
-
+// clazy:excludeall=non-pod-global-static
 static const std::string base64_chars = 
              "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
              "abcdefghijklmnopqrstuvwxyz"