Name conflicts in stubs

[acru3l]

Hi :)

Sibyl by default includes two stubs: win_api_x86_32.py and linux_stdlib.py. Both stubs define different functions with the same name: get_fmt_args. But this breaks some of the stub functions in win_api_x86_32.py that call get_fmt_args, e.g. msvcrt_sprintf with the following error:

TypeError: get_fmt_args() takes exactly 3 arguments (4 given)

To avoid this issue, we have to specify a stub file explicitly.