Merge #1451: changelog: add entry for "field: Remove x86_64 asm"

d2e36a2 changelog: add entry for "field: Remove x86_64 asm" (Jonas Nick)

Pull request description:

ACKs for top commit:
  real-or-random:
    ACK d2e36a2

Tree-SHA512: c4bffb921c58185b0a43546977449f3c53c21230d6d32cf5d5ccf563b196ec3d0370a0b87de5b334e5190ff91da598dd0bbebbb5c9d7bef9ec8c0679c3b6c702

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 #### Changed
  - The point multiplication algorithm used for ECDH operations (module `ecdh`) was replaced with a slightly faster one.
+ - Optional handwritten x86_64 assembly for field operations was removed because modern C compilers are able to output more efficient assembly. This change results in a significant speedup of some library functions when handwritten x86_64 assembly is enabled (`--with-asm=x86_64` in GNU Autotools, `-DSECP256K1_ASM=x86_64` in CMake), which is the default on x86_64. Benchmarks with GCC 10.5.0 show a 10% speedup for `secp256k1_ecdsa_verify` and `secp256k1_schnorrsig_verify`.
+
 
 ## [0.4.0] - 2023-09-04