Add secp256k1_ec_grind to grind keypairs #507

1. 
   sipa commented at 1:24 am on February 9, 2018: contributor

   Unsure if this should be in upstream, but it may be useful for things like shaving off a few bytes from signatures.
2. nym-zone referenced this in commit 83ff9bde8f on Feb 13, 2018
3. nym-zone referenced this in commit 23c560aa94 on Feb 13, 2018
4. 
   kallewoof commented at 11:57 am on July 2, 2018: member

   Tested ACK 885ea63

   This PR is used as is in https://github.com/kallewoof/btcdeb/tree/vanitygen – I verified that the keypair is valid.

   I grinded bc1qkallealmkdwwyuc2tmf5c6hzmlaujq6jl38hpe using this, and sent myself 10k goodly satoshi, which a wallet with the imported private key saw in its balance, and could sign transactions for. "ismine": true also appeared in getaddressinfo output. As Nicolas Dorier would put it, I ate my own (@sipa’s, rather) dog food.

5. sipa force-pushed on Sep 17, 2021
6. sipa force-pushed on Sep 17, 2021
7. sipa force-pushed on Sep 20, 2021
8. Add secp256k1_ec_grind to grind keypairs. 28a87ee9e5
9. sipa force-pushed on Sep 20, 2021
10. sipa added the label feature on May 11, 2023

Contributors
sipa kallewoof

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feature