Add in and out parameters to doxygen #418

[matter123]

Resolves #418

[jeff-hykin]

are spaces allowed?

/*!
 * @param[ out] dest
 versus
 * @param[out] dest
 */
void memcpy(void *dest, const void *src, size_t n);

[matter123]

I haven't seen one with spaces, but I haven't looked particularly long.

Regardless, I don't think it will hurt.

Edit: added support for spaces.