auto merge of #14764 : jbcrail/rust/fix-more-comments, r=alexcrichton

diff --cc src/libgreen/context.rs
Simple merge

diff --cc src/librustc/middle/trans/base.rs
Simple merge

diff --cc src/librustc/middle/typeck/variance.rs
Simple merge

diff --cc src/librustdoc/html/markdown.rs
Simple merge