tidy-up: syntax and code nits

- cmp-pkg-config.sh: replace `-r -f` with `-rf` to match rest of repo.
- configure.ac: add double quotes for robustness (not a bug).
- curl-openssl.m4: merge nested `if`s.
- CurlTests.c: drop `!= 0`, also to sync with m4.
- CurlTests.c: replace `example.com` with `localhost` in
  `gethostbyname()` feature test code. (compile-only, not a bug)
- GHA/http3-linux: drop literal `true` from bool expression.
- lib650: drop redundant `&`.
- move variable/call to left-hand side of equality checks, where
  missing.
- perl: detach `<`/`>` from filename in `open()`, where missing.
- schannel: apply two nit fixes lost in rebase.
- scripts/verify-release: drop redundant double quotes.
- scripts/verify-release: exit with error code on error.
- synctime: replace magic numbers with `sizeof()`.
- telnet: add missing parentheses to macro value.
- tests/Makefile.am: use single quotes.
- tool_operate: drop redundant `break` after `return` in VMS code.
- unit2413: drop unused NULL pointer + free call.
- unit2413: fix duplicate test case name.
- urlapi: drop redundant parentheses.
- urlapi: drop `CURL_UNCONST()` that became redundant.

Closes #22186

scripts/badwords

@@ -149,7 +149,7 @@ sub sourcecode {
     my $flags = 0;
     my @lines;
     my $line;
-    open(F, "<$f");
+    open(F, "<", $f);
     while(<F>) {
         my $l = $_;
         ($state, $flags, $line) = srcline($state, $flags, $l);
@@ -175,7 +175,7 @@ my %wl;
 my @w;
 my @exact;
 my $file = shift @ARGV;
-open(CONFIG, "<$file") or die "Cannot open '$file': $!";
+open(CONFIG, "<", $file) or die "Cannot open '$file': $!";
 while(<CONFIG>) {
     chomp;
     if($_ =~ /^#/) {
@@ -261,7 +261,7 @@ sub highlight {
 sub document {
     my ($f) = @_;
     my @lines;
-    open(F, "<$f");
+    open(F, "<", $f);
     while(<F>) {
         push @lines, $_;
     }