perf tools: Improve 'libbabel' feature check failure message

On Debian-ish systems libbabeltrace-dev should be suggested as a package
install as well.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: David Ahern <david.ahern@oracle.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20150228091849.GA28959@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>