Check compiletime library version
check_compiletime_version:"2.1.6"

Check runtime library version
check_runtime_version:"2.1.6"

Check for MBEDTLS_VERSION_C
check_feature:"MBEDTLS_VERSION_C":0

Check for MBEDTLS_AES_C when already present
depends_on:MBEDTLS_AES_C
check_feature:"MBEDTLS_AES_C":0

Check for unknown define
check_feature:"MBEDTLS_UNKNOWN":-1