Merge branch 'auxv' into 'master'

Implement auxiliary vector

See merge request redox-os/syscall!53

src/flag.rs

@@ -291,6 +291,11 @@ bitflags! {
     }
 }
 
+// Auxiliery vector types
+pub const AT_NULL: usize = 0;
+pub const AT_PHDR: usize = 3;
+pub const AT_ENTRY: usize = 9;
+
 bitflags! {
     pub struct WaitFlags: usize {
         const WNOHANG =    0x01;