bug #43 "replace" 7.0 & 5.6 polyfills (nicolas-grekas)

This PR was merged into the 3.3 branch.

Discussion
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"replace" 7.0 & 5.6 polyfills

This removes `paragonie/random_compat`, `symfony/polyfill-php70` and  `symfony/polyfill-apcu` from minimal install - they are not needed since PHP 7.0.
And removes  `symfony/polyfill-php56` for deps that would need it (eg symfony/security).

ext-iconv is already an implicit requirement for Symfony.

Commits
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bbee2c3 "replace" 7.0 & 5.6 polyfills

Author: fabpot

composer.json

@@ -5,6 +5,7 @@
     "description": "Project description",
     "require": {
         "php": "^7.0.8",
+        "ext-iconv": "*",
         "symfony/console": "^3.3",
         "symfony/flex": "^1.0",
         "symfony/framework-bundle": "^3.3",
@@ -29,6 +30,11 @@
             "App\\Tests\\": "tests/"
         }
     },
+    "replace": {
+        "symfony/polyfill-apcu": "*",
+        "symfony/polyfill-php70": "*",
+        "symfony/polyfill-php56": "*"
+    },
     "scripts": {
         "auto-scripts": [
         ],