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

docs/examples/htmltitle.cpp

@@ -46,9 +46,9 @@
 //
 
 #ifdef _WIN32
-#define COMPARE(a, b) (!_stricmp((a), (b)))
+#define COMPARE(a, b) (!_stricmp(a, b))
 #else
-#define COMPARE(a, b) (!strcasecmp((a), (b)))
+#define COMPARE(a, b) (!strcasecmp(a, b))
 #endif
 
 //