CRC calculation

[AT0myks]

Another finding from testing. calc_crc returns a wrong result for a significant number of files. The summary is:

Before the last 2 PRs:

• 4 errors (RLN36)
• 58 ok
• 356 bad

Now:

• 0 errors
• 61 ok
• 357 bad

The section count fix only helped in 3 cases.

Here are the results in case they're useful. The keys are the sha256 of the PAK file. crc32 is the CRC from the file and calc_crc the result from the function.