use strbuf_addstr() for adding constant strings to a strbuf, part 2

use strbuf_addstr() for adding constant strings to a strbuf, part 2

Replace uses of strbuf_addf() for adding strings with more lightweight
strbuf_addstr() calls.  This makes the intent clearer and avoids
potential issues with printf format specifiers.

02962d36845b89145cd69f8bc65e015d78ae3434 already converted six cases,
this patch covers eleven more.

A semantic patch for Coccinelle is included for easier checking for
new cases that might be introduced in the future.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>