t: fix Lexer line count for $() inside double-quoted strings

scan_dqstring's post-loop newline counter re-counts newlines that
were already counted during recursive parsing of $() bodies.  This
happens because scan_dollar returns text containing newlines (from
multi-line command substitutions), and the catch-all counter at the
end of scan_dqstring counts all of them again.

Fix this by counting newlines inline as non-special characters are
consumed, and removing the post-loop catch-all.  Each newline is
now counted exactly once: literal newlines at the inline match,
line splices at the backslash handler, and $() newlines by
scan_token during the recursive parse.

This does not affect chainlint's output because chainlint annotates
the original body text using byte offsets, not token line numbers.
It matters for greplint.pl (introduced in a subsequent commit) which
uses token line numbers to report the source location of bare grep
assertions.

Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>

Author: mmontalbo

t/lib-shell-parser.pl

@@ -93,8 +93,13 @@ sub scan_dqstring {
 	my $b = $self->{buff};
 	my $s = '"';
 	while (1) {
-		# slurp up non-special characters
-		$s .= $1 if $$b =~ /\G([^"\$\\]+)/gc;
+		# slurp up non-special characters; count newlines inline
+		# so $() newlines (counted by scan_token during recursive
+		# parsing) are not double-counted by a post-loop catch-all.
+		if ($$b =~ /\G([^"\$\\]+)/gc) {
+			$s .= $1;
+			$self->{lineno} += () = $1 =~ /\n/sg;
+		}
 		# handle special characters
 		last unless $$b =~ /\G(.)/sgc;
 		my $c = $1;
@@ -111,7 +116,6 @@ sub scan_dqstring {
 		}
 		die("internal error scanning dq-string '$c'\n");
 	}
-	$self->{lineno} += () = $s =~ /\n/sg;
 	return $s;
 }