[SecurityBundle] reference individual security-* packages

Author: nicolas-grekas

src/Symfony/Bundle/SecurityBundle/composer.json

@@ -19,9 +19,12 @@
         "php": "^7.1.3",
         "ext-xml": "*",
         "symfony/config": "^4.2",
-        "symfony/security": "~4.2",
         "symfony/dependency-injection": "^4.2",
-        "symfony/http-kernel": "^4.1"
+        "symfony/http-kernel": "^4.1",
+        "symfony/security-core": "~4.2",
+        "symfony/security-csrf": "~4.2",
+        "symfony/security-guard": "~4.2",
+        "symfony/security-http": "~4.2"
     },
     "require-dev": {
         "symfony/asset": "~3.4|~4.0",