fix: revert '+' syntax optimize && add growth check limit for 'random_recursive_mutation'

[0x7Fancy]

for issue #42, I revert '+' syntax optimize

for issue #43, Grammar-Mutator has to rely on AST to work, in the case of TOKEN conflicts, grammar parsing may fail. at the same time, Grammar-Mutator will try to retain data for nodes that fail to parse. If the depth of the syntax tree is large and grammar parsing errors occur, it may cause random_recursive_mutation to be mutated each time. the data size exceeds 1024 bytes, thus falling into do-while. I added an failed limit for this.

[h1994st]

LGTM. Thanks!

A kind reminder: please merge to dev branch next time :)

[vanhauser-thc]

@h1994st when are you pushing to stable? so I can update in the AFL++ repository :)

[h1994st]

@vanhauser-thc I can do it now, as there are unlikely new updates recently

[h1994st]

@h1994st when are you pushing to stable? so I can update in the AFL++ repository :)

Done.

[vanhauser-thc]

thank you!