Fix single-line-style paragraph fills with code immediately before or after
Move the rt::io::process tests to run-pass

Closes #9341
auto merge of #9578 : alexcrichton/rust/un-ignore-libuv-process-tests, r=brson

Closes #9341
auto merge of #9600 : MicahChalmer/rust/fill-with-code-around, r=catamorphism

This fixes a problem with paragraph fills: hitting M-q on a single-line-style (`//`) comment with code immediately before or after it would try to fill the code as part of the paragraph too.