Idea list

Let's collect some ideas on how to improve the grammar mutator.
I am not an expert on this, so some ideas might be not possible, no sense or even makes things worse.

* Use the dictionary with the grammar (-x + LTO AUTODICT feature)
* Increase the tree depth with every new cycle without finds (example on how to pass this to the mutator is in examples/honggfuzz/honggfuzz.c)
* ... ?

Also:
document for a mutation which mutation strategies were used, and if it results in a new path, crash or hang, document these away somewhere (fopen("a")... fwrite() ... fclose() would be fine enough), and learn which types are more effective than others, and then try to improve them. maybe weighting, maybe changing how unsuccessful techniques work, etc. (and of course this feature with an #ifdef TESTING or something like that.

pinging @h1994st @andreafioraldi @eqv for more ideas