message: Use fallible conversion in getpagesize()
diff: //! unistd implementation for Redox, following http://pubs.opengroup.org/onlinepubs/7908799/xsh/unistd.h.html
  +use core::convert::TryFrom;
  use core::{mem, ptr, slice};
  use c_str::CStr;
  @@ -334,7 +335,21 @@ pub extern "C" fn getlogin_r(name: *mut c_char, namesize: size_t) -> c_int {
  #[no_mangle]
  pub extern "C" fn getpagesize() -> c_int {
  - sysconf(_SC_PAGESIZE) as c_int
  + match c_int::try_from(sysconf(_SC_PAGESIZE)) {
  + Ok(page_size) => page_size,
  + Err(_) => {
  + /* Behavior not specified by POSIX for this case. The -1
  + * value mimics sysconf()'s behavior, though.
  + *
  + * As specified for the limits.h header, the minimum
  + * acceptable value for {PAGESIZE} is 1. The -1 value thus
  + * cannot be mistaken for an acceptable value.
  + *
  + * POSIX does not specify any possible errors for this
  + * function, hence no errno setting. */
  + -1
  + }
  + }
  }
  // #[no_mangle]
  