Implement API for configuration of opaque PSKs
Implement API for configuration of opaque PSKs

This commit adds implementations of the two new API functions

mbedtls_ssl_conf_psk_opaque()
mbedtls_ssl_set_hs_psk_opaque().

ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls