updated for mbed-os 5.5

Revision:
2:75cff722e9d3
Child:
3:82771b5493b3
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Tue Jul 11 14:51:04 2017 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/mbed-os/#50b3418e45484ebf442b88cd935a2d5355402d7d