Recursive mod include causes rustc to crash.

[acertain]

test.rs:

mod test;
fn main(){}

causes

rust: task 7f855ac0c250 ran out of stack
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug
note: try running with RUST_LOG=rustc=1,::rt::backtrace to get further details and report the results to github.com/mozilla/rust/issues
rust: task failed at 'explicit failure', /private/tmp/rust-GCHx/rust-0.6/src/librustc/rustc.rc:357
rust: domain main @0x7f855b009810 root task failed

[jdm]

Duplicate of #5711.