tidy-up: miscellaneous

- GHA/checkdocs: rename `spellcheck` job to `pyspelling` to say
  the exact tool used.
- GHA/checkdocs: restore a comment.
- GHA/linux: add `-B .` to a cmake configure to avoid warning, and
  future breakage.
- autotools: use correct casing for `Schannel`.
- doh: update RFC URL.
- drop redundant parenthesis.
- fix indentation, whitespace.

Closes #18756

.github/workflows/checkdocs.yml

@@ -100,8 +100,8 @@ jobs:
       - name: 'mdlinkcheck'
         run: ./scripts/mdlinkcheck
 
-  spellcheck:
-    name: 'spellcheck'
+  pyspelling:
+    name: 'pyspelling'
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5
@@ -125,6 +125,7 @@ jobs:
       - name: 'check spelling'
         run: |
           source ~/venv/bin/activate
+          # setup the custom wordlist
           grep -v '^#' .github/scripts/spellcheck.words > wordlist.txt
           aspell --version
           pyspelling --version