perf tools: Make Ctrl-C stop processing on TUI

It was inconvenient that perf cannot be quit with SIGINT during
processing samples on TUI especially for large data files.

This was because the first argument of SLang_init_tty(), abort_char,
being 0.  The manual says it's the ascii value of the control character
that will be used to generate the interrupt signal [1].  Passing -1
means to use the default value (Ctrl-C).

However, after processing samples, Ctrl-C was used to in other cases as
well - like stepping back from annotate.  So recover the original
behavior after processing.

[1] http://jedsoft.org/slang/doc/html/cslang-6.html#ss6.1

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1432904024-13170-1-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>