Optimaze with new mbed os for study

Dependencies:   TS_DISCO_F746NG BSP_DISCO_F746NG Graphics

Revision:
5:64cafb3c6e7b
diff -r 66f13188c26b -r 64cafb3c6e7b mbed-os.lib
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Fri Aug 23 16:59:22 2019 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/mbed-os/#73f096399b4cda1f780b140c87afad9446047432