REL: Prepare for the NumPy 1.21.4 release.

- Create the 1.21.4-changelog.rst file.
- Update the 1.21.4-notes.rst file.

doc/changelog/1.21.4-changelog.rst

@@ -0,0 +1,27 @@
+
+Contributors
+============
+
+A total of 7 people contributed to this release.  People with a "+" by their
+names contributed a patch for the first time.
+
+* Bas van Beek
+* Charles Harris
+* Isuru Fernando
+* Matthew Brett
+* Sayed Adel
+* Sebastian Berg
+* 傅立业（Chris Fu） +
+
+Pull requests merged
+====================
+
+A total of 7 pull requests were merged for this release.
+
+* `#20278 <https://github.com/numpy/numpy/pull/20278>`__: BUG: Fix shadowed reference of `dtype` in type stub
+* `#20293 <https://github.com/numpy/numpy/pull/20293>`__: BUG: Fix headers for universal2 builds
+* `#20294 <https://github.com/numpy/numpy/pull/20294>`__: BUG: ``VOID_nonzero`` could sometimes mutate alignment flag
+* `#20295 <https://github.com/numpy/numpy/pull/20295>`__: BUG: Do not use nonzero fastpath on unaligned arrays
+* `#20296 <https://github.com/numpy/numpy/pull/20296>`__: BUG: Distuils patch to allow for 2 as a minor version (!)
+* `#20297 <https://github.com/numpy/numpy/pull/20297>`__: BUG, SIMD: Fix 64-bit/8-bit integer division by a scalar
+* `#20298 <https://github.com/numpy/numpy/pull/20298>`__: BUG, SIMD: Workaround broadcasting SIMD 64-bit integers on MSVC...

doc/source/release/1.21.4-notes.rst

@@ -4,42 +4,42 @@
 NumPy 1.21.4 Release Notes
 ==========================
 
+The NumPy 1.21.4 is a maintenance release that fixes a few bugs discovered
+after 1.21.3. The most important fix here is a fix for the NumPy header files
+to make them work for both x86_64 and M1 hardware when included in the Mac
+universal2 wheels. Previously, the header files only worked for M1 and this
+caused problems for folks building x86_64 extensions. This problem was not seen
+before Python 3.10 because there were thin wheels for x86_64 that had
+precedence. This release also provides thin x86_64 Mac wheels for Python 3.10.
 
-Highlights
-==========
+The Python versions supported in this release are 3.7-3.10. If you want to
+compile your own version using gcc-11, you will need to use gcc-11.2+ to avoid
+problems.
 
 
-New functions
-=============
-
-
-Deprecations
+Contributors
 ============
 
+A total of 7 people contributed to this release.  People with a "+" by their
+names contributed a patch for the first time.
 
-Future Changes
-==============
+* Bas van Beek
+* Charles Harris
+* Isuru Fernando
+* Matthew Brett
+* Sayed Adel
+* Sebastian Berg
+* 傅立业（Chris Fu） +
 
-
-Expired deprecations
+Pull requests merged
 ====================
 
+A total of 7 pull requests were merged for this release.
 
-Compatibility notes
-===================
-
-
-C API changes
-=============
-
-
-New Features
-============
-
-
-Improvements
-============
-
-
-Changes
-=======
+* `#20278 <https://github.com/numpy/numpy/pull/20278>`__: BUG: Fix shadowed reference of `dtype` in type stub
+* `#20293 <https://github.com/numpy/numpy/pull/20293>`__: BUG: Fix headers for universal2 builds
+* `#20294 <https://github.com/numpy/numpy/pull/20294>`__: BUG: ``VOID_nonzero`` could sometimes mutate alignment flag
+* `#20295 <https://github.com/numpy/numpy/pull/20295>`__: BUG: Do not use nonzero fastpath on unaligned arrays
+* `#20296 <https://github.com/numpy/numpy/pull/20296>`__: BUG: Distuils patch to allow for 2 as a minor version (!)
+* `#20297 <https://github.com/numpy/numpy/pull/20297>`__: BUG, SIMD: Fix 64-bit/8-bit integer division by a scalar
+* `#20298 <https://github.com/numpy/numpy/pull/20298>`__: BUG, SIMD: Workaround broadcasting SIMD 64-bit integers on MSVC...