Add rusage constants

src/sys_resource/src/lib.rs

@@ -9,6 +9,11 @@ extern crate sys_time;
 use platform::types::*;
 use sys_time::timeval;
 
+pub const RUSAGE_SELF: c_int = 0;
+pub const RUSAGE_CHILDREN: c_int = -1;
+pub const RUSAGE_BOTH: c_int = -2;
+pub const RUSAGE_THREAD: c_int = 1;
+
 type rlim_t = u64;
 
 #[repr(C)]