perf annotate browser: Show 'jumpy' functions

Just press 'J' and see how many places jump to jump targets.

The hottest jump target appears in red, targets with more than one
source have a different color than single source jump targets.

Suggested-by: Arjan van de Ven <arjan@infradead.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-7452y0dmc02a20ooins7rn79@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>