added I2C control function (Original program cannot handle I2C constructor)

Dependencies:   TextLCD X_NUCLEO_53L0A1

Fork of HelloWorld_53L0A1 by ST

Revision:
13:5a59de800135
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Tue Feb 06 10:14:16 2018 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/mbed-os/#caeaa49d68c67ee00275cece10cd88e0ed0f6ed3