Don't define stdio functions in coexist-with-libc mode.

In coexist-with-libc mode, we don't control the layout of the `FILE`
struct, so don't try to implement the stdio functions.

c-scape/src/lib.rs

@@ -102,6 +102,7 @@ mod pty;
 mod rand_;
 mod regex;
 mod sort;
+#[cfg(feature = "take-charge")]
 mod stdio;
 mod strtod;
 mod strtol;