make some sort of c or cython submodule to wrap variadic args

[lifning]

a callback of type retro_log_printf_t must accept variable arguments after the format string:

typedef void (RETRO_CALLCONV *retro_log_printf_t)(enum retro_log_level level,
const char *fmt, ...);

ctypes can't handle 'em because libffi doesn't support 'em.
so we miss out on a lot of nice logging from cores by default.

[lifning]

first pass exists in dev branch