perf tools: Add time-based utility functions

Add function to parse a user time string of the form <start>,<stop>
where start and stop are time in sec.nsec format. Both start and stop
times are optional.

Add function to determine if a sample time is within a given time
time window of interest.

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1480439746-42695-2-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index b2a47aa..bdad82a 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -87,6 +87,7 @@
 libperf-y += mem-events.o
 libperf-y += vsprintf.o
 libperf-y += drv_configs.o
+libperf-y += time-utils.o
 
 libperf-$(CONFIG_LIBBPF) += bpf-loader.o
 libperf-$(CONFIG_BPF_PROLOGUE) += bpf-prologue.o