auto merge of #16982 : jbcrail/rust/comment-and-string-corrections, r=alexcrichton

I corrected spelling and capitalization errors in comments and strings.

diff --cc src/liblibc/lib.rs
Simple merge

diff --cc src/libregex/lib.rs
Simple merge

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

diff --cc src/libstd/io/mod.rs
Simple merge

diff --cc src/libsyntax/ext/format.rs
Simple merge