fdo#76260 - Switch from vector to std::stack.

std::stack uses std::deque which is extremely expensive for this case.
This change saves 43bn of 98bn cycles spent in createFastChildContext.

Change-Id: I63919a9826563171f128e09d7206ac6cfdde336f

writerfilter/source/ooxml/OOXMLFastContextHandler.cxx

@@ -179,7 +179,7 @@ bool OOXMLFastContextHandler::prepareMceContext(Token_t nElement, const uno::Ref
                 m_bDiscardChildren = false;
                 aState.m_bTookChoice = m_bTookChoice;
                 m_bTookChoice = false;
-                m_aSavedAlternateStates.push(aState);
+                m_aSavedAlternateStates.push_back(aState);
             }
             break;
         case OOXML_Choice:
@@ -241,8 +241,8 @@ throw (uno::RuntimeException, xml::sax::SAXException, std::exception)
         m_bDiscardChildren = false;
     else if (Element == (NS_mce | OOXML_AlternateContent))
     {
-        SavedAlternateState aState(m_aSavedAlternateStates.top());
-        m_aSavedAlternateStates.pop();
+        SavedAlternateState aState(m_aSavedAlternateStates.back());
+        m_aSavedAlternateStates.pop_back();
         m_bDiscardChildren = aState.m_bDiscardChildren;
         m_bTookChoice = aState.m_bTookChoice;
     }

writerfilter/source/ooxml/OOXMLFastContextHandler.hxx

@@ -290,7 +290,7 @@ private:
     uno::Reference< uno::XComponentContext > m_xContext;
     bool m_bDiscardChildren;
     bool m_bTookChoice; ///< Did we take the Choice or want Fallback instead?
-    std::stack<SavedAlternateState> m_aSavedAlternateStates;
+    std::vector<SavedAlternateState> m_aSavedAlternateStates;
 
     static sal_uInt32 mnInstanceCount;