Define PHP 7.4 token constants for downgraded build

[TomasVotruba]

Problem

The released tool is downgraded to PHP 7.2, but the bundled nikic/php-parser references PHP 7.4 token constants directly. On a real 7.2 runtime this fatals on boot:

PHP Fatal error: Uncaught Error: Undefined constant 'T_BAD_CHARACTER'
  in vendor/nikic/php-parser/lib/PhpParser/ParserAbstract.php:155

(plus constant(): Couldn't find constant T_FN / T_COALESCE_EQUAL warnings)

php-parser ships compatibility_tokens.php, but it only polyfills PHP 8.0+ tokens — the 7.4 ones (T_FN, T_COALESCE_EQUAL, T_BAD_CHARACTER) are assumed to always exist, which is not true once the tool is downgraded to 7.2.

Fix

Define the three missing 7.4 token constants in the bin entry point, guarded by defined() so it is a no-op on PHP 7.4+. Same approach ECS uses in bin/ecs.php.

Verification

Ran the patched build on a real PHP 7.2.34 against a project — previously fatal, now:

[OK] No conflicts found in 17130 files

[TomasVotruba]

LGTM, let's ship

[TomasVotruba]

Inspiration from: https://github.com/easy-coding-standard/ecs/blob/main/bin/ecs.php#L86-L97

[samsonasik]

imo, this should be equal with php 8.+ values:

php > echo T_FN;
311
php > echo T_COALESCE_EQUAL;
367
php > echo T_BAD_CHARACTER;
409

[TomasVotruba]

It doesn't really matter, as it's a placeholder value. If it's not existing token value.

5xxx are reserved