Replace magic number with readable sig constant

SIG_ERR is defined as 'pub const SIG_ERR: sighandler_t = !0 as sighandler_t;'

Author: anatol

src/libstd/sys/unix/mod.rs

@@ -92,7 +92,7 @@ pub fn init() {
 
     #[cfg(not(any(target_os = "nacl", target_os = "emscripten", target_os="fuchsia")))]
     unsafe fn reset_sigpipe() {
-        assert!(signal(libc::SIGPIPE, libc::SIG_IGN) != !0);
+        assert!(signal(libc::SIGPIPE, libc::SIG_IGN) != libc::SIG_ERR);
     }
     #[cfg(any(target_os = "nacl", target_os = "emscripten", target_os="fuchsia"))]
     unsafe fn reset_sigpipe() {}