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, $_;
     }

scripts/cd2cd

@@ -212,7 +212,7 @@ HEAD
     close(F);
 
     if($inplace) {
-        open(O, ">$f") or return 1;
+        open(O, ">", $f) or return 1;
         print O @desc;
         close(O);
     }

scripts/managen

@@ -1047,7 +1047,7 @@ sub header {
 sub sourcecategories {
     my ($dir) = @_;
     my %cats;
-    open(H, "<$dir/../../src/tool_help.h") or
+    open(H, "<", "$dir/../../src/tool_help.h") or
         die "cannot find the header file";
     while(<H>) {
         if(/^\#define CURLHELP_([A-Z0-9]*)/) {

scripts/mk-ca-bundle.pl

@@ -257,7 +257,7 @@ sub sha256 {
 
 sub oldhash {
     my $hash = "";
-    open(C, "<$_[0]") or return 0;
+    open(C, "<", $_[0]) or return 0;
     while(<C>) {
         chomp;
         if($_ =~ /^\#\# SHA256: (.*)/) {

scripts/verify-release

@@ -39,14 +39,14 @@ tarball="${1:-}"
 
 if [ -z "$tarball" ]; then
   echo "Provide a curl release tarball name as argument"
-  exit
+  exit 1
 fi
 
 i="$(find . -maxdepth 1 -type d -name 'curl-*' | wc -l)"
 
 if test "$i" -gt 1; then
   echo "multiple curl-* entries found, disambiguate please"
-  exit
+  exit 1
 fi
 
 # check if this is in a git clone directory
@@ -115,7 +115,7 @@ else
     mv "$f" _tarballs/
   done
 fi
-cd "_tarballs"
+cd _tarballs
 
 # compare the new tarball against the original
 sha256sum -c checksum