fmt_double() may write up to 8 characters into its format_str[]
buffer, which however only has room for 7 characters.

This case could be triggered by a call to erts_printf_format() with
any floating-point format that also includes #, and + or a space,
which may be uncommon, but a nif or driver could issue it.

Sign character was not accounted for.

Ex:
float_to_list(-3.1265538967899625e+69, [{decimals,16}]).

* maint:
  Bump version of crash dumps to 0.4
  Verify that binaries of different sizes are dumped correctly
  Don't dump literal areas that are not referenced at all
  Dump literals separately to avoid incomplete heap data
  Implement dumping of maps in crash dumps
  Buffer writing of crash dumps

Conflicts:
	erts/emulator/beam/erl_alloc.types

Writing of crash dumps were done using unbuffered IO. This
is slow since many small writes are done.

Use a FILE* with an allocated buffer to obtain buffered IO.

I wrote a small test program that created 50000 binaries of 200 bytes
each and then created a crash dump. The crash dumping was an order of
magnitude faster with buffered IO than without.

This refactor was done using the unifdef tool like this:
    for file in $(find erts/ -name *.[ch]); do unifdef -t -f defile -o $file $file; done

where defile contained:
    #define ERTS_SMP 1
    #define USE_THREADS 1
    #define DDLL_SMP 1
    #define ERTS_HAVE_SMP_EMU 1
    #define SMP 1
    #define ERL_BITS_REENTRANT 1
    #define ERTS_USE_ASYNC_READY_Q 1
    #define FDBLOCK 1
    #undef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
    #define ERTS_POLL_ASYNC_INTERRUPT_SUPPORT 0
    #define ERTS_POLL_USE_WAKEUP_PIPE 1
    #define ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE 1
    #undef ERTS_HAVE_PLAIN_EMU
    #undef ERTS_SIGNAL_STATE

This behaviour has been seen when using docker together with --cpuset-cpus.