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

.github/scripts/cmp-config.pl

@@ -136,6 +136,5 @@ foreach my $v (keys %remove) {
     }
 }
 
-
 # return the exit code from diff
 exit system("diff -u /tmp/autotools /tmp/cmake") >> 8;

.github/scripts/randcurl.pl

@@ -116,7 +116,6 @@ my %commonrc = (
     '26' => 1,
     );
 
-
 sub runone {
     my $a;
     my $nargs = getnum(60) + 1;

.github/scripts/spacecheck.pl

@@ -39,6 +39,13 @@ my @need_crlf = (
     "\\.(bat|sln)\$",
 );
 
+my @double_empty_lines = (
+    "^lib/.+\\.(c|h)\$",
+    "^packages/",
+    "^tests/data/test",
+    "\\.(m4|py)\$",
+);
+
 my @non_ascii_allowed = (
     '\xC3\xB6',  # UTF-8 for https://codepoints.net/U+00F6 LATIN SMALL LETTER O WITH DIAERESIS
 );
@@ -100,7 +107,7 @@ while(my $filename = <$git_ls_files>) {
     my @err = ();
 
     if(!fn_match($filename, @tabs) &&
-        $content =~ /\t/) {
+       $content =~ /\t/) {
         push @err, "content: has tab";
     }
 
@@ -111,12 +118,12 @@ while(my $filename = <$git_ls_files>) {
     }
 
     if($eol ne "crlf" &&
-        fn_match($filename, @need_crlf)) {
+       fn_match($filename, @need_crlf)) {
         push @err, "content: must use CRLF EOL for this file type";
     }
 
     if($eol ne "lf" && $content ne "" &&
-        !fn_match($filename, @need_crlf)) {
+       !fn_match($filename, @need_crlf)) {
         push @err, "content: must use LF EOL for this file type";
     }
 
@@ -131,20 +138,27 @@ while(my $filename = <$git_ls_files>) {
     }
 
     if($content ne "" &&
-        $content !~ /\n\z/) {
+       $content !~ /\n\z/) {
         push @err, "content: has no EOL at EOF";
     }
 
     if($content =~ /\n\n\z/ ||
-        $content =~ /\r\n\r\n\z/) {
+       $content =~ /\r\n\r\n\z/) {
         push @err, "content: has multiple EOL at EOF";
     }
 
     if($content =~ /\n\n\n\n/ ||
-        $content =~ /\r\n\r\n\r\n\r\n/) {
+       $content =~ /\r\n\r\n\r\n\r\n/) {
         push @err, "content: has 3 or more consecutive empty lines";
     }
 
+    if(!fn_match($filename, @double_empty_lines)) {
+        if($content =~ /\n\n\n/ ||
+           $content =~ /\r\n\r\n\r\n/) {
+            push @err, "content: has 2 consecutive empty lines";
+        }
+    }
+
     if($content =~ /([\x00-\x08\x0b\x0c\x0e-\x1f\x7f])/) {
         push @err, "content: has binary contents";
     }

.github/scripts/verify-synopsis.pl

@@ -39,7 +39,6 @@ sub testcompile {
     return $rc;
 }
 
-
 sub extract {
     my($f) = @_;
     my $syn = 0;