perf tools: Move get_term_dimensions from top to util.c

It is used by util/help.c so it should be a lib function and included in
libperf.a. Code move only.

Signed-off-by: David Ahern <dsahern@gmail.com>
Link: http://lkml.kernel.org/r/1358185681-90926-1-git-send-email-dsahern@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>