Merge branch 'escalated_consume' into 'master'

Use call rather than close in final escalated step.

See merge request redox-os/relibc!641

src/platform/redox/exec.rs

@@ -291,7 +291,16 @@ pub fn execve(
         // over this process (unless it fails). We do this manually since drop cannot handle
         // errors.
         let fd = *escalate_fd as usize;
-        core::mem::forget(escalate_fd);
+        unsafe {
+            syscall::syscall5(
+                syscall::SYS_CALL,
+                fd,
+                0,
+                0,
+                syscall::CallFlags::CONSUME.bits(),
+                0,
+            )?;
+        }
 
         syscall::close(fd)?;