datatop: polling interval change

Make dtop_poll_periodically wait the time it takes to poll so that the
polling times are more accurate to the second.

Change-Id: I3253deb79c60b76bc7c0fa8823678832979d2ed0
diff --git a/datatop/src/Android.mk b/datatop/src/Android.mk
index f4b4b43..51d062a 100644
--- a/datatop/src/Android.mk
+++ b/datatop/src/Android.mk
@@ -21,6 +21,7 @@
 LOCAL_CFLAGS := -Wall -Wextra -Werror -pedantic
 LOCAL_CFLAGS += -DVERSION="\"1.0.4"\"
 LOCAL_CFLAGS += -DHAVE_STRL_FUNCTIONS
+LOCAL_CFLAGS += -D _BSD_SOURCE
 
 LOCAL_C_INCLUDES := $(LOCAL_PATH)