bug#26347: patch for mwheel.el

[Tak Kunihiro]

>>>>> During not only horizontal scroll but also vertical scroll,
>>>>> `auto-hscroll-mode' should be disabled by following three aspects.
>>>>> 
>>>>> (1) It should be off during horizontal scroll.  If it is on, scope
>>>>>   jumps randomly when point is at the edge.  Also, since
>>>>>   horizontal scroll does not move point, there will be
>>>>>   inconsistency between point and scope, and the inconsistency
>>>>>   will result in unexpected shift of the scope.
>>>>> 
>>>> We don't turn off auto-hscroll-mode when scrolling with the horizontal
>>>> or vertical scroll bars, and we don't have the problems you describe
>>>> in those cases.  Why is this case different?
>>> 
>>> I see your point in regard to (1).  Yes, if `mwheel-scroll’ can scroll right
>>> or left like horizontal-scroll-bar does, turing off auto-hscroll-mode is not
>>> necessary for case (1).  Give me time to understand code of 
>>> horizontal-scroll-bar.
>> 
>> I see (1) is true for Emacs 25.1 on Mac and Emacs 24.5 on Windows
>> but Emacs 25.1 on Windows.
>
> Did you mean Emacs 24.5 on Windows but _not_ Emacs 25.1 on Windows?

Let me take it back and rephrase.  I meant (1) is true for Emacs 24.5
on Windows but not for Emacs 25.1 on Windows.  Emacs 25.1 on Windows
scrolls horizontally well with auto-hscroll-mode on.