Change Details

``` Fixes #823. ``` Backport 1/11 of sepc256k1 PR830. Note: the first `memcmp()` in `recovery/tests_impl.h` was removed in D2193. Depends on D8036.

``` Fixes #823. ``` Backport 1/11 of secp256k1 PR830: https://github.com/bitcoin-core/secp256k1/pull/830/commits/6173839c90553385171d560be8a17cbe167e3bef Note: the first `memcmp()` in `recovery/tests_impl.h` was removed in D2193. Depends on D8036.

``` Fixes #823. ``` Backport 1/11 of sepccp256k1 PR830.: https://github.com/bitcoin-core/secp256k1/pull/830/commits/6173839c90553385171d560be8a17cbe167e3bef Note: the first `memcmp()` in `recovery/tests_impl.h` was removed in D2193. Depends on D8036.