Rollup of 5 pull requests - #59653

Closed

Centril wants to merge 14 commits into

rust-lang:masterfrom

Centril:rollup-0kr2w0l

Commits on Mar 11, 2019

Add initial implementation of 'sort_at_index' for slices -- analog to C++'s std::nth_element (a.k.a. quickselect)
Mokosha
committed
3f306db

Commits on Mar 29, 2019

improve worst-case performance of BTreeSet difference and intersection
ssomers
committed
f5fee8f

Commits on Apr 1, 2019

wasi: Load arguments via syscalls
alexcrichton
committed
382f9a7
wasi: Use raw syscalls for stdio
alexcrichton
committed
60f6cbd
wasi: Implement `error_string` to get readable errors
alexcrichton
committed
32a7684

Commits on Apr 2, 2019