Merge branch 'ctime_r' into 'master'

added ctime_r

See merge request redox-os/relibc!250

src/header/time/mod.rs

@@ -138,11 +138,14 @@ pub unsafe extern "C" fn ctime(clock: *const time_t) -> *mut c_char {
     asctime(localtime(clock))
 }
 
-// #[no_mangle]
-pub extern "C" fn ctime_r(clock: *const time_t, buf: *mut c_char) -> *mut c_char {
-    unimplemented!();
+#[no_mangle]
+pub unsafe extern "C" fn ctime_r(clock: *const time_t, buf: *mut c_char) -> *mut c_char {
+    let mut tm1 : tm = core::mem::uninitialized();
+    localtime_r(clock, &mut tm1);
+    asctime_r(&mut tm1, buf)
 }
 
+
 #[no_mangle]
 pub extern "C" fn difftime(time1: time_t, time0: time_t) -> c_double {
     (time1 - time0) as c_double