Rollup merge of rust-lang#49184 - bdrewery:update-beta-freebsd, r=alexcrichton

Update beta to version with fixed FreeBSD support from rust-lang#49023.

Fixes rust-lang#42681

r? @alexcrichton

Author: kennytm

src/stage0.txt

@@ -12,7 +12,7 @@
 # source tarball for a stable release you'll likely see `1.x.0` for rustc and
 # `0.x.0` for Cargo where they were released on `date`.
 
-date: 2018-02-20
+date: 2018-03-18
 rustc: beta
 cargo: beta