Integrate tlshc library, calculate telfhash and import hash in ELF module

[HoundThe]

This PR integrates the tlshc library https://github.com/avast/tlshc that provides a C implementation of the TLSH hashing function https://github.com/trendmicro/tlsh, calculates Telfhash using the TLSH hashing function, and also creates a simple MD5 hash of imported symbols for ELF files.

[HoundThe]

Some tests were failing due to the usage of md5_ctx in import_md5 not being hidden in case there is no crypto lib to support it.

[dmknght]

The current tlsh library of Avast is missing important feature: calculate 2 hashes and give the score.
The original code has this method int totalDiff(const Tlsh *, bool len_diff=true) const;. However, there's no function like that in https://github.com/avast/tlshc/blob/main/include/tlshc/tlsh.h. Therefore, current hash comparison in Yara module is based on exact hash matching. It's not good IMO.
To use this method / function with Yara, the tlsh module needs to convert a hash from text to a struct's data. Therefore the method int fromTlshStr(const char* str); is required. It's also missing in Avast's module.
I created 2 issues on Avast's repository about 2 missing functions. Hope they update this soon.
avast/tlshc#1
avast/tlshc#2