tidy-up: miscellaneous

- drop stray duplicate empty lines in docs, scripts, test data, include,
  examples, tests.
- drop duplicate PP parenthesis.
- curl-functions.m4: move literals to the right side in if expressions,
  to match rest of the source code.
- FAQ.md: delete language designator from an URL.
- packages: apply clang-format (OS400, VMS).
- scripts/schemetable.c: apply clang-format.
- data320: delete duplicate empty line that doesn't change the outcome.
- spacecheck: extend to check for duplicate empty lines
  (with exceptions.)
- fix whitespace nits

Closes #19936

scripts/firefox-db2pem.sh

@@ -54,7 +54,6 @@ cat > "$out" <<EOF
 ##
 EOF
 
-
 certutil -L -h 'Builtin Object Token' -d "$db" | \
 grep ' *[CcGTPpu]*,[CcGTPpu]*,[CcGTPpu]* *$' | \
 sed -e 's/ *[CcGTPpu]*,[CcGTPpu]*,[CcGTPpu]* *$//' -e 's/\(.*\)/"\1"/' | \