Explicitly initialize global storage containers

This commit changes initialization of the global storage containers to be
explicit instead of happening during static initialization. This makes the
containers properly initialized if PythonQt is initialized and cleaned up more
than once.

The motivation for this change is to support testing cleanup and finalization.

Author: msmolens

src/PythonQt.cpp

@@ -1294,6 +1294,10 @@ PythonQtPrivate::PythonQtPrivate()
   _hadError = false;
   _systemExitExceptionHandlerEnabled = false;
   _debugAPI = new PythonQtDebugAPI(this);
+
+  PythonQtConv::global_valueStorage.init();
+  PythonQtConv::global_ptrStorage.init();
+  PythonQtConv::global_variantStorage.init();
 }
 
 void PythonQtPrivate::setupSharedLibrarySuffixes()

src/PythonQtMisc.h

@@ -76,12 +76,25 @@ template <typename T, int chunkEntries> class PythonQtValueStorage
   PythonQtValueStorage() {
     _chunkIdx  = 0;
     _chunkOffset = 0;
+    _currentChunk = NULL;
+  };
+
+  //! initialize memory
+  void init() {
+    assert(_currentChunk == NULL);
+    assert(_chunks.isEmpty());
+    _chunkIdx = 0;
+    _chunkOffset = 0;
     _currentChunk = new T[chunkEntries];
     _chunks.append(_currentChunk);
-  };
+  }
 
   //! clear all memory
   void clear() {
+    _chunkIdx = 0;
+    _chunkOffset = 0;
+    _currentChunk = NULL;
+
     T* chunk;
     Q_FOREACH(chunk, _chunks) {
       delete[]chunk;