prevent optimization in algorithms
Add secure_erase function to clear secrets
Update the function with good practices
Renaming random.h to examples_util.h
Signed-off-by: Harshil Jani <harshiljani2002@gmail.com>
This is a backport of [[https://github.com/bitcoin-core/secp256k1/pull/1212 | secp256k1#1212]]