Combine simple masks

[mfr-itr]

I generated a mask set for 8+ characters. A lot of these marks are very small, so hashcat spends a lot of time starting and stopping jobs, leading to a sub-optimal workload (1Ghash / 40Ghash). I think it would be more efficient to combine similar masks, like "...?l", "...?u" and "...?d" could be combined into "...?a". Even if the keyspace is larger, it may end quickly (TODO : benchmark).
BTW, for small keyspaces like <= 6 chars and sufficient compute power, a full bruteforce lasts a few seconds so there is no need to add specific masks for small passwords.