fix for issue 1118: check if iv is zero in gcm.
fix for issue 1118: check if iv is zero in gcm.

1) found by roberto in mbedtls forum
2) if iv_len is zero, return an error
3) add tests for invalid parameters

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