starmath: IndexOfSubNode() is for SmStructureNode only

... not for the base class.

Change-Id: I9f6a6de93a4db964c8b019349049fdef4afaf224
Reviewed-on: https://gerrit.libreoffice.org/26583
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Takeshi Abe <tabe@fixedpoint.jp>
diff --git a/starmath/inc/node.hxx b/starmath/inc/node.hxx
index bde97d5..f6f684d 100644
--- a/starmath/inc/node.hxx
+++ b/starmath/inc/node.hxx
@@ -205,17 +205,6 @@ public:
        mpParentNode = parent;
    }

    /** Get the index of a child node
     *
     * Returns -1, if pSubNode isn't a subnode of this.
     */
    int IndexOfSubNode(SmNode* pSubNode){
        sal_uInt16 nSize = GetNumSubNodes();
        for(sal_uInt16 i = 0; i < nSize; i++)
            if(pSubNode == GetSubNode(i))
                return i;
        return -1;
    }
    /** Set the token for this node */
    void SetToken(SmToken& token){
        maNodeToken = token;
@@ -313,6 +302,19 @@ public:

    virtual void  GetAccessibleText( OUStringBuffer &rText ) const override;

    /** Get the index of a child node
     *
     * Returns -1, if pSubNode isn't a subnode of this.
     */
    int IndexOfSubNode(SmNode* pSubNode)
    {
        sal_uInt16 nSize = GetNumSubNodes();
        for(sal_uInt16 i = 0; i < nSize; i++)
            if(pSubNode == GetSubNode(i))
                return i;
        return -1;
    }

    void SetSubNode(size_t nIndex, SmNode* pNode)
    {
        size_t size = aSubNodes.size();