Rollup merge of rust-lang#503 - Idolf:fix-mode, r=gnzlbg

Set the type for S_ISUID, S_ISGID and S_ISVTX correctly

Author: gnzlbg

src/unix/mod.rs

@@ -229,9 +229,9 @@ pub const GRPQUOTA: ::c_int = 1;
 
 pub const SIGIOT: ::c_int = 6;
 
-pub const S_ISUID: ::c_int = 0x800;
-pub const S_ISGID: ::c_int = 0x400;
-pub const S_ISVTX: ::c_int = 0x200;
+pub const S_ISUID: ::mode_t = 0x800;
+pub const S_ISGID: ::mode_t = 0x400;
+pub const S_ISVTX: ::mode_t = 0x200;
 
 pub const IF_NAMESIZE: ::size_t = 16;
 pub const IFNAMSIZ: ::size_t = IF_NAMESIZE;