riched20: Add tests for ITextRange interface.

[Caibin Chen]

The ITextRange objects are returned by ITextDocument_Range() method.
Both IRichEditOle and ITextService supports ITextDocument interface.
Currently we don't have ITextDocument support in ITextService. my
another patch[1] is to add ITextDocument interface support in
ITextService.

[1]. http://www.winehq.org/pipermail/wine-patches/2013-July/125258.html

2013/7/18 Nikolay Sivov <bunglehead at gmail.com>:
> On 7/18/2013 23:36, Caibin Chen wrote:
>>
>> ITextRange will be used in both richole.c and txtsrv.c. I'm planning
>> to add more tests in it. I think it makes more sense to have one test
>> file for each interface, which improves the readability of tests.
>
> That's usually done for implementation, but not for the tests. What does it
> mean it will be used in both files by the way?
>
>>
>> 2013/7/18 Nikolay Sivov <bunglehead at gmail.com>:
>>>
>>> On 7/18/2013 20:28, Caibin Chen wrote:
>>>>
>>>> Add tests for start and end point, setting and getting text.
>>>> ---
>>>>    dlls/riched20/tests/Makefile.in |   3 +-
>>>>    dlls/riched20/tests/txtrng.c    | 343
>>>> ++++++++++++++++++++++++++++++++++++++++
>>>>    2 files changed, 345 insertions(+), 1 deletion(-)
>>>>    create mode 100644 dlls/riched20/tests/txtrng.c
>>>
>>> You could just use existing file, richole.c fits I think.
>>>
>