benches/ is broken

[termoshtt]

$ cargo +nightly bench
   Compiling sfmt v0.7.0 (/home/teramura/rhq/github.com/rust-math/sfmt)
error[E0433]: failed to resolve: use of undeclared type `XorShiftRng`
  --> benches/rand_gen.rs:27:31
   |
27 |     def_bench!(xorshift, f64, XorShiftRng::from_entropy());
   |                               ^^^^^^^^^^^ use of undeclared type `XorShiftRng`

error[E0433]: failed to resolve: use of undeclared type `XorShiftRng`
  --> benches/rand_gen.rs:33:31
   |
33 |     def_bench!(xorshift, f32, XorShiftRng::from_entropy());
   |                               ^^^^^^^^^^^ use of undeclared type `XorShiftRng`

error[E0433]: failed to resolve: use of undeclared type `XorShiftRng`
  --> benches/rand_gen.rs:39:31
   |
39 |     def_bench!(xorshift, u64, XorShiftRng::from_entropy());
   |                               ^^^^^^^^^^^ use of undeclared type `XorShiftRng`

error[E0433]: failed to resolve: use of undeclared type `XorShiftRng`
  --> benches/rand_gen.rs:45:31
   |
45 |     def_bench!(xorshift, u32, XorShiftRng::from_entropy());
   |                               ^^^^^^^^^^^ use of undeclared type `XorShiftRng`

For more information about this error, try `rustc --explain E0433`.

maybe due to https://github.com/rust-math/sfmt/commit/e43e1db3ee9e944021153914120918cb5070d555

[termoshtt]

The above error is fixed in #30, but nightly rust cannot be used because of #36