Modify the cfmakeraw() wrapper to handle its return type on AIX

[xingxue-ibm]

On AIX, the signature of cfmakeraw() differs in that its return type is int instead of void. When the argument termios_p is NULL, it returns -1. Otherwise, it returns 0.

int cfmakeraw(struct termios *termios_p);

We believe it is safe to ignore the return value and have modified the cfmakeraw() wrapper to account for this difference.

[sunfishcode]

Thanks!

[sunfishcode]

This is now released in rustix 1.1.1.