Clean up old ICU version checks

Since 1.36, intl has been a required PHP extension, and PHP 7.4 dropped
support for ICU < 50.1 (Unicode 6.2), so:

* In SpecialVersion, don't check whether INTL_ICU_VERSION is defined.

* Remove check in the installer for outdated Unicode normalization. It
  was added over twelve years ago in r70126 (a21fb8651f20f1ef) with a
  comment that it should be kept up to date, but no one ever did.

* Remove IcuCollation::getUnicodeVersionForICU(), which contained a long
  list of ICU versions and corresponding Unicode versions that had to be
  kept up to date manually. Instead use IntlChar::getUnicodeVersion(),
  which was added in PHP 7.0. There are no known callers outside core.

* Remove LinkFilter::supportsIDN(), as ICU has had support for UTS#46
  since version 4.6. There are no known callers outside core. Also
  remove $flags and $variant from the idn_to_utf8() call, which match
  PHP 7.4's defaults. (INTL_IDNA_VARIANT_2003 was the default in 7.3.)

* Display the ICU and Unicode versions in the installer, just below the
  PHP version. The ICU version is shown on Special:Version near the PHP
  version, and it probably makes sense to show it there as well.

Change-Id: Ibdfac1a6f46fd56b84de1140292e0ec863f043ee

1 files changed, 1 insertions, 3 deletions

diff --git a/maintenance/refreshExternallinksIndex.php b/maintenance/refreshExternallinksIndex.php
index 87e5f4cc6a4f..49a09e444803 100644
--- a/maintenance/refreshExternallinksIndex.php
+++ b/maintenance/refreshExternallinksIndex.php
@@ -39,9 +39,7 @@ class RefreshExternallinksIndex extends LoggedUpdateMaintenance {
 	}
 
 	protected function getUpdateKey() {
-		return static::class
-			. ' v' . LinkFilter::VERSION
-			. ( LinkFilter::supportsIDN() ? '+' : '-' ) . 'IDN';
+		return static::class . ' v' . LinkFilter::VERSION . '+IDN';
 	}
 
 	protected function updateSkippedMessage() {