message: implemented fputc, fputs, and puts
diff: @@ -105,12 +105,22 @@ pub extern "C" fn fopen(filename: *const c_char, mode: *const c_char) -> *mut FI
  #[no_mangle]
  pub extern "C" fn fputc(c: c_int, stream: *mut FILE) -> c_int {
  - unimplemented!();
  + platform::FileWriter(stream as c_int).write_char(c as u8 as char).map_err(|_| return -1);
  + c
  }
  #[no_mangle]
  -pub extern "C" fn fputs(s: *const c_char, stream: *mut FILE) -> c_int {
  - unimplemented!();
  +pub unsafe extern "C" fn fputs(s: *const c_char, stream: *mut FILE) -> c_int {
  + extern "C" {
  + fn strlen(s: *const c_char) -> size_t;
  + }
  + use core::{ str, slice };
  + let len = strlen(s);
  + platform::FileWriter(stream as c_int).write_str(str::from_utf8_unchecked(slice::from_raw_parts(
  + s as *const u8,
  + len,
  + ))).map_err(|_| return -1);
  + len as i32
  }
  #[no_mangle]
  @@ -245,8 +255,9 @@ pub unsafe extern "C" fn putchar_unlocked(c: c_int) -> c_int {
  }
  #[no_mangle]
  -pub extern "C" fn puts(s: *const c_char) -> c_int {
  - unimplemented!();
  +pub unsafe extern "C" fn puts(s: *const c_char) -> c_int {
  + fputs(s, stdout);
  + putchar(b'\n' as c_int)
  }
  #[no_mangle]
  