auto merge of #14481 : alexcrichton/rust/no-format-strbuf, r=sfackler

* Removes `format_strbuf!()`

diff --cc src/librustc/back/link.rs
Simple merge

diff --cc src/librustc/middle/check_match.rs
Simple merge

diff --cc src/librustc/middle/mem_categorization.rs
Simple merge

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

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

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

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

diff --cc src/librustdoc/clean/mod.rs
Simple merge

diff --cc src/libstd/str.rs
Simple merge