Fix updatedb bug with Drush 9, and allow site-local Drush 8. (#4425)

* Revert dependencies back to what they were in Drush 8.3.2.

* Allow symfony/var-dumper:^5

* Remove update_fix_compatibility(), as in Drush 10. This method does not exist in Drupal 9. See https://www.drupal.org/node/3026100

commands/core/drupal/update.inc

@@ -133,7 +133,11 @@ function update_main() {
   require_once DRUPAL_ROOT . '/core/includes/install.inc';
   require_once DRUPAL_ROOT . '/core/includes/update.inc';
   drupal_load_updates();
-  update_fix_compatibility();
+
+  // Disables extensions that have a lower Drupal core major version, or too high of a PHP requirement.
+  // Those are rare, and this function does a full rebuild. So commenting it out as in Drush 10.
+  // n.b. This function does not exist in Drupal 9. See https://www.drupal.org/node/3026100
+  // update_fix_compatibility();
 
   // Check requirements before updating.
   if (!drush_update_check_requirements()) {

composer.json

@@ -39,7 +39,7 @@
     "consolidation/annotated-command": "^2.12.0",
     "consolidation/output-formatters": "~3",
     "symfony/yaml": "~2.3|^3|^4.4",
-    "symfony/var-dumper": "~2.7|^3|^4.4",
+    "symfony/var-dumper": "~2.7|^3|^4.4|^5",
     "symfony/console": "~2.7|^3|^4.4",
     "symfony/event-dispatcher": "~2.7|^3|^4.4",
     "symfony/finder": "~2.7|^3|^4.4",
@@ -55,7 +55,8 @@
     "symfony/finder": "~2.7",
     "symfony/yaml": "~2.3",
     "phpunit/phpunit": "4.*",
-    "symfony/process": "2.7.*"
+    "symfony/process": "2.7.*",
+    "symfony/var-dumper": "2.8.*"
   },
   "suggest": {
       "ext-pcntl": "*",