Sonar example with callbacks.

Revision:
0:1713cdc51510
diff -r 000000000000 -r 1713cdc51510 mbed-os.lib
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Thu Sep 07 22:17:59 2017 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/mbed-os/#98ba8acb83cfc65f30a8a0771a27c71443ab093a