Merge pull request #197 from volcano0dr/master

Add struct ucred definition in sgx_libc. Thanks to @volcano0dr !

sgx_libc/src/linux/x86_64/mod.rs

@@ -136,6 +136,7 @@ pub type gid_t = u32;
 pub type ino64_t = u64;
 pub type nfds_t = c_ulong;
 pub type pthread_t = c_ulong;
+pub type pid_t = i32;
 
 #[derive(Copy, Clone, Debug)]
 pub enum DIR {}
@@ -400,6 +401,12 @@ s! {
         pub pw_dir: *mut c_char,
         pub pw_shell: *mut c_char,
     }
+
+    pub struct ucred {
+        pub pid: pid_t,
+        pub uid: uid_t,
+        pub gid: gid_t,
+    }
 }
 
 pub const AT_FDCWD: c_int = -100;