Overlapping chunks caused by incorrect skip/limit combination

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Previous calculation of limit caused overlap in chunks. The limit flag does not limit to X words from the start, but rather "Limit X words from the start + skipped words" (according to hashcat manual).

In practical terms, I have observed the following:

Chunk 0: S = 0, L = 500000 (words: 0-500000) Chunk 1: S = 500000, L = 1000000 (words 500000 - 1500000, but should be words 500000 - 1000000, chunk is 2 x intended size) Chunk 2: S = 1000000, L = 1500000 (words 1000000 - 2500000, but should be words 1000000 - 2500000, chunk is 3 x intended size) etc.

I have adjusted chunk/skip calculation to reflect this. Removed limit variable entirely, as it was just a copy of chunk_size, neither of which change during the command building.

Please see #357 for a fix.

I'm not using a distributed setup currently, so I'm probably going to just set the chunk size much higher to avoid chunking anyway. I would like to request the ability to disable the chunking: if you're only running on one system, chunking does not give any benefit that I can see and prevents you seeing an estimated time of completion for each task.

[GrepItAll]

Here is an example of this. The limit should always be 1000000 in my case as I have set that as the chunk size.