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

lib/optiontable.pl

@@ -77,7 +77,6 @@ sub add {
     }
 }
 
-
 my $fl;
 while(<STDIN>) {
     my $l = $_;
@@ -122,7 +121,6 @@ while(<STDIN>) {
     }
 }
 
-
 for my $name (sort @names) {
     my $oname = $name;
     my $a = $alias{$name};