[PATCH v5] msvcrt: Don't crash if _vsnwprintf gets NULL as format string and add test

[Piotr Caban]

Hi Fabian,

On 11/27/17 22:12, Fabian Maurer wrote:
>   dlls/msvcr90/tests/msvcr90.c | 31 +++++++++++++++++++++++++++++++
>   dlls/msvcrt/printf.h         |  3 +++
>   2 files changed, 34 insertions(+)

It doesn't compile cleanly (wine64):
../../../../wine_src/dlls/msvcr90/tests/msvcr90.c: In function 
'_vsnwprintf_wrapper':
../../../../wine_src/dlls/msvcr90/tests/msvcr90.c:1874:43: warning: 
passing argument 4 of 'p__vsnwprintf' from incompatible pointer type 
[-Wincompatible-pointer-types]
      ret = p__vsnwprintf(str, len, format, valist);
                                            ^~~~~~
../../../../wine_src/dlls/msvcr90/tests/msvcr90.c:1874:43: note: 
expected '__va_list_tag *' but argument is of type '__builtin_ms_va_list 
{aka char *}'

Thanks,
Piotr