article: Add const qualifier to pointer variables in local scope

[ma8ma]

ローカルのポインター変数にconstを付けられるとcppcheckに指摘されたため修正します。

cppcheck 2.11.1のレポート

src/article/toolbar.cpp:62:22: style: Variable 'articleview' can be declared as pointer to const [constVariablePointer]
    ArticleViewBase* articleview = dynamic_cast< ArticleViewBase* >( view );
                     ^
src/article/drawareabase.cpp:603:29: style: Variable 'css' can be declared as pointer to const [constVariablePointer]
        CORE::CSS_PROPERTY* css = m_layout_tree->get_separator()->css;
                            ^
src/article/drawareabase.cpp:604:20: style: Variable 'rect' can be declared as pointer to const [constVariablePointer]
        RECTANGLE* rect = m_layout_tree->get_separator()->rect;
                   ^
src/article/drawareabase.cpp:4296:16: style: Variable 'rect_from' can be declared as pointer to const [constVariablePointer]
    RECTANGLE* rect_from = layout->rect;
               ^
src/article/drawareabase.cpp:4442:13: style: Variable 'layout' can be declared as pointer to const [constVariablePointer]
    LAYOUT* layout = caret_pos.layout;
            ^
src/article/articleadmin.cpp:643:21: style: Variable 'view' can be declared as pointer to const [constVariablePointer]
    SKELETON::View* view = get_current_view();
                    ^