Add mbed-client-c to mbed-client
Add mbed-client-c to mbed-client

Adding mbed-client-c (without mbed-coap) to mbed-client to pull in
all dependencies for applications due to coap-separation change
in mbedOS 5.4.

ARMmbed/mbed-client,tridonic-com/mbed-client,tridonic-com/mbed-client,tridonic-com/mbed-client,ARMmbed/mbed-client,ARMmbed/mbed-client