chained editeng: Add TextChainFlow related files

<https://cgit.freedesktop.org/libreoffice/core/commit/?id=4c33aa61b3ea1fa170b9446fbfdffe85b659ff3b>:

> commit 4c33aa61b3ea1fa170b9446fbfdffe85b659ff3b
> Author: matteocam <matteo.campanelli@gmail.com>
> Date:   Sun Sep 6 11:29:03 2015 +0200
>
>     chained editeng: Add TextChainFlow related files
>
>     Change-Id: I0e4155391fff29dc4484c7aedd4e62f02c4afd25
[...]
> diff --git a/svx/source/svdraw/textchainflow.cxx b/svx/source/svdraw/textchainflow.cxx
> new file mode 100644
> index 0000000..922cfb3
> --- /dev/null
> +++ b/svx/source/svdraw/textchainflow.cxx
[...]
> +/*
> + * Check for overflow in the state of pFlowOutl.
> + * If pParamOutl is not NULL sets some parameters from there.
> + * This is useful in case the outliner is not set for overflow
> + * (e.g. in editing mode we check for overflow in drawing outl but
> + *  parameters come from editing outliner)
> +*/
> +void TextChainFlow::impCheckForFlowEvents(SdrOutliner *pFlowOutl, SdrOutliner *pParamOutl)
> +{
> +    bool bOldUpdateMode = pFlowOutl->GetUpdateMode();
> +
> +    // XXX: This could be reorganized moving most of this stuff inside EditingTextChainFlow
> +    if (pParamOutl != NULL)
> +    {
> +        // We need this since it's required to check overflow
> +        pFlowOutl->SetUpdateMode(true);
> +
> +        // XXX: does this work if you do it before setting the text? Seems so.
> +        impSetFlowOutlinerParams(pFlowOutl, pParamOutl);
> +    }
> +
> +    bool bIsPageOverflow = pFlowOutl->IsPageOverflow();
> +
> +    // NOTE: overflow and underflow cannot be both true
> +    bOverflow = bIsPageOverflow && mpNextLink;
> +    bUnderflow = !bIsPageOverflow &&  mpNextLink && mpNextLink->HasText();
> +
> +    // Get old state on whether to merge para-s or not
> +    // NOTE: We handle UF/OF using the _old_ state. The new one is simply saved
> +    bool bMustMergeParaAmongLinks = GetTextChain()->GetIsPartOfLastParaInNextLink(mpTargetLink);
> +
> +    // Set (Non)OverflowingTxt here (if any)
> +
> +    // If we had an underflow before we have to deep merge paras anyway
> +    bool bMustMergeParaOF = bMustMergeParaAmongLinks || mbOFisUFinduced;
> +
> +    // XXX
> +    bMustMergeParaOF = true; // XXX: Experiment: no deep merging.

should that be removed?

> +
> +    mpOverflChText = bOverflow ?
> +                     new OFlowChainedText(pFlowOutl, bMustMergeParaOF) :
> +                     NULL;
[...]