Rollup of 7 pull requests#59397

Merged

bors merged 16 commits intorust-lang:masterfrom

Mar 24, 2019

Commits on Feb 16, 2019

implement nth_back for Box
koalatux
committed

Commits on Feb 23, 2019

implement nth_back for Windows
koalatux
committed

Commits on Mar 15, 2019

Track changes to robots.txt
kornelski
committed

Commits on Mar 17, 2019

Use a valid name for graphviz graphs
matthewjasper
committed

Commits on Mar 19, 2019

Do not encode gensymed imports in metadata
petrochenkov
committed

Commits on Mar 21, 2019

Fix undefined behavior in hint::spin_loop for x86 targets without SSE2
gnzlbg
committed

Commits on Mar 22, 2019

Fix ICE with const generic param in struct
varkor
committed

Commits on Mar 23, 2019

Commits on Mar 24, 2019