Improve hash search with ideas from delsum

[trufae]

This stuff was implemented in radare more than 15 years ago, but nobody cared about that stuff, so probably makes sense to revamp it with inspiration from projects like this:

• https://github.com/8051Enthusiast/delsum

[0x00000000]> /h?
| /h[?*] [algorithm] [digest] [size]  find block of size bytes having this digest. See ph
[0x00000000]>

[trufae]

cc @sylvainpelissier