Auto merge of #1774 - jtgeibel:update/tar-and-flate, r=sgrif

Update `tar`, `flate2`, and `libflate`

Begin bisecting the segfault caused by a bulk `cargo update` by only
bumping a few dependencies.

`cargo update -p flate2:0.2.20 -p flate2:1.0.7 -p libflate -p tar --aggressive`

Author: bors