Since librdkafka's callbacked based consumption combined with
auto-commit of offsets results in low offset storage granularity
it is better if kafkacat explicitly stores offsets per-message.

Refactored bootstrap.sh script (fsaintjacques)

- removed '|| exit 1' pattern by using correct bash options
- safe usage of variables

Tee mode & RPM spec by fsaintjacques

- origlen renamed to orig_len, types to size_t and declared a top
- use CONF_T_TEE + conf.flags instead of a new field

According to the man page:

On success, fread() and fwrite() return the number of items read or written.
This number equals the number of bytes transferred only when size is 1. If an
error occurs, or the end of the file is reached, the return value is a short
item count (or zero).

Credits goes to David Haguenauer for this catch.

Adds an option for the producer to emit sent messages to
stdout, thus emulating tee.

Topic error reporting bugfix (vencik)