When SIGSEGV or SIGFPE reaches the tarantool we try to gather
all information related to the crash and print it out to the
console (well, stderr actually). Still there is a request
to not just show this info locally but send it out to the
feedback server.

Thus to keep gathering crash related information in one module,
we move fatal signal handling into the separate crash.c file.
This allows us to collect the data we need in one place and
reuse it when we need to send reports to stderr (and to the
feedback server, which will be implemented in next patch).

Part-of #5261

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>