Sorry deium,
I am not sure about the MRAA_PIN_FAST_GPIO stuff and/or which version of the library the new stuff has/is propagated with.
The new faster speed stuff, is by using memory mapped mode for a pin. You enable it by using the function:
mraa_gpio_use_mmaped(mraa_gpio_context dev, mraa_boolean_t mmap)
Where you pass in the pin context and a non zero value for mmap... I assume they also added the same method to the C++ wrapper as well.