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/delta

@@ -95,7 +95,7 @@ my $deletes=`git diff-tree --diff-filter=A -r --summary origin/$branch $start 2>
 my $creates=`git diff-tree --diff-filter=D -r --summary origin/$branch $start 2>/dev/null | wc -l`;
 
 # Time since that tag
-my $tagged=`git for-each-ref --format="%(refname:short) | %(taggerdate:unix)" refs/tags/* | grep ^$start | cut "-d|" -f2`; # Unix timestamp
+my $tagged=`git for-each-ref --format="%(refname:short) | %(taggerdate:unix)" refs/tags/* | grep ^$start | cut '-d|' -f2`; # Unix timestamp
 my $taggednice=`git for-each-ref --format="%(refname:short) | %(creatordate)" refs/tags/* | grep ^$start | cut '-d|' -f2`; # human readable time
 chomp $taggednice;
 my $now=POSIX::strftime("%s", localtime());