php.extensions.pcs: Mark broken in 7.3, add tokenizer dependency

The pcs extension fails to load at runtime with PHP 7.3, so let's mark
it broken from 7.3 onwards. It also depends on the tokenizer internal
extension.

pkgs/top-level/php-packages.nix

@@ -562,8 +562,10 @@ in
 
       sha256 = "0d4p1gpl8gkzdiv860qzxfz250ryf0wmjgyc8qcaaqgkdyh5jy5p";
 
+      internalDeps = [ php.extensions.tokenizer ];
+
       meta.maintainers = lib.teams.php.members;
-      meta.broken = isPhp74; # Build error
+      meta.broken = isPhp73; # Runtime failure on 7.3, build error on 7.4
     };
 
     pdo_oci = buildPecl rec {