Merge branch 'rs/export-strbuf-addchars'

Code clean-up.

* rs/export-strbuf-addchars:
  strbuf: use strbuf_addchars() for adding a char multiple times
  strbuf: export strbuf_addchars()

diff --cc Documentation/technical/api-strbuf.txt
Simple merge

diff --cc merge-recursive.c
Simple merge

diff --cc pretty.c
Simple merge

diff --cc strbuf.c
Simple merge

diff --cc strbuf.h
Simple merge

diff --cc utf8.c
Simple merge