tidy-up: miscellaneous

- badwords: replace stray synonyms with 'null-terminator'.
- tests/FILEFORMAT.md: tidy up feature descriptions.
- printf: replace stray `%i` masks with `%d` for consistency.
- pytest: add comments for empty excepts to try silencing GitHub CodeQL
  warnings.
- tool1394, unit1675: merge nested `if`s.
- dnscache: fix typo in comment.
- fix whitespace, indent and newlines.

Closes #21921

m4/curl-compilers.m4

@@ -862,6 +862,7 @@ AC_DEFUN([CURL_SET_COMPILER_WARNING_OPTS], [
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [conditional-uninitialized])
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [language-extension-token])
           fi
+
           dnl Only clang 3.1 or later
           if test "$compiler_num" -ge "301"; then
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [format-non-iso])
@@ -883,6 +884,7 @@ AC_DEFUN([CURL_SET_COMPILER_WARNING_OPTS], [
                 ;;
             esac
           fi
+
           dnl Only clang 3.3 or later
           if test "$compiler_num" -ge "303"; then
             tmp_CFLAGS="$tmp_CFLAGS -Wno-documentation-unknown-command"
@@ -914,38 +916,46 @@ AC_DEFUN([CURL_SET_COMPILER_WARNING_OPTS], [
               tmp_CFLAGS="$tmp_CFLAGS -Wno-varargs"
             fi
           fi
+
           dnl clang 7 or later
           if test "$compiler_num" -ge "700"; then
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [assign-enum])
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [extra-semi-stmt])
           fi
+
           dnl clang 10 or later
           if test "$compiler_num" -ge "1000"; then
             tmp_CFLAGS="$tmp_CFLAGS -Wimplicit-fallthrough"  # we have silencing markup for clang 10.0 and above only
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [xor-used-as-pow])
           fi
+
           dnl clang 13 or later
           if test "$compiler_num" -ge "1300"; then
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [cast-function-type])
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [reserved-identifier]) # Keep it before -Wno-reserved-macro-identifier
             tmp_CFLAGS="$tmp_CFLAGS -Wno-reserved-macro-identifier"  # Sometimes such external macros need to be set
           fi
+
           dnl clang 16 or later
           if test "$compiler_num" -ge "1600"; then
             tmp_CFLAGS="$tmp_CFLAGS -Wno-unsafe-buffer-usage"
           fi
+
           dnl clang 17 or later
           if test "$compiler_num" -ge "1700"; then
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [cast-function-type-strict])  # with Apple clang it requires 16.0 or above
           fi
+
           dnl clang 19 or later
           if test "$compiler_num" -ge "1901"; then
             tmp_CFLAGS="$tmp_CFLAGS -Wno-format-signedness"
           fi
+
           dnl clang 20 or later
           if test "$compiler_num" -ge "2001"; then
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [array-compare])
           fi
+
           dnl clang 21 or later
           if test "$compiler_num" -ge "2101"; then
             CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [c++-hidden-decl])