perf tools: Move TUI-specific fields out of map_symbol

The has_children and unfolded fields don't belong to the struct
map_symbol since they're used by the TUI only.  Move those fields out of
map_symbol since the struct is also used by other places.

This will also help to compact the sizeof struct hist_entry.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
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/1429687101-4360-11-git-send-email-namhyung@kernel.org
Link: http://lkml.kernel.org/r/1430837746-5439-1-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>