Merge bitcoin-core/secp256k1#1309: changelog: Catch up

697e1cc changelog: Catch up (Tim Ruffing)
76b43f3 changelog: Add entry for bitcoin#1303 (Tim Ruffing)

Pull request description:

ACKs for top commit:
  sipa:
    ACK 697e1cc
  jonasnick:
    ACK 697e1cc

Tree-SHA512: cfeb513effc69925bdedd3a298b1e2e5bf7709f68b453a5f157c584560b5400c3dc8b9ce87a775281cdea9db7f44e7e1337fbc93563f6efe350fe5defacbc4f6

CHANGELOG.md

@@ -7,9 +7,19 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+#### Security
+ - Module `ecdh`: Fix "constant-timeness" issue with GCC 13.1 (and potentially future versions of GCC) that could leave applications using libsecp256k1's ECDH module vulnerable to a timing side-channel attack. The fix avoids secret-dependent control flow during ECDH computations when libsecp256k1 is compiled with GCC 13.1.
+
 #### Fixed
  - Fixed an old bug that permitted compilers to potentially output bad assembly code on x86_64. In theory, it could lead to a crash or a read of unrelated memory, but this has never been observed on any compilers so far.
 
+#### Changed
+ - Various improvements and changes to CMake builds. CMake builds remain experimental.
+   - Made API versioning consistent with GNU Autotools builds.
+   - Switched to `BUILD_SHARED_LIBS` variable for controlling whether to build a static or a shared library.
+   - Added `SECP256K1_INSTALL` variable for the controlling whether to install the build artefacts.
+ - Renamed asm build option `arm` to `arm32`. Use `--with-asm=arm32` instead of `--with-asm=arm` (GNU Autotools), and `-DSECP256K1_ASM=arm32` instead of `-DSECP256K1_ASM=arm` (CMake).
+
 ## [0.3.1] - 2023-04-10
 We strongly recommend updating to 0.3.1 if you use or plan to use Clang >=14 to compile libsecp256k1, e.g., Xcode >=14 on macOS has Clang >=14. When in doubt, check the Clang version using `clang -v`.