[msvc] Application crashes when rendering a video

[L1itrer]

Trying to render a video on windows when compiling with msvc crashes the application. The video is created but it's a black screen with only music.

[L1itrer]

Okay I investigated it and it seems that the problem is with a malloc call in "ffmpeg_windows.c". There is no #include <stdlib.h> and it seems that the microsoft c compiler when missing the malloc definition uses some variant of the function which returns an int rather than void*.
I found a similiar case on stackoverflow: https://stackoverflow.com/questions/33393633/access-violation-after-malloc

Including stdlib.h does seem to fix the issue. I was going to submit a pull request but the fix is so simple that it seems like an overkill.