utils/strbuf: Added SDB_STRBUF_STR.
utils/strbuf: Added SDB_STRBUF_STR.

This macro returns a tuple describing the buffer content and length. The idea
is that functions which operate on (binary) strings should accept two such
arguments and the macro will make it easier to pass them in.

sysdb/sysdb,sysdb/sysdb,tokkee/sysdb,tokkee/sysdb,sysdb/sysdb,tokkee/sysdb