minor #116 Php70: do not expose intArg (glensc)

This PR was merged into the 1.8-dev branch.

Discussion
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Php70: do not expose intArg

`Php70::intArg` is used from `Php70` class only. make it private.

project search result: https://github.com/symfony/polyfill/search?q=intArg&type=Code

Commits
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c36388c Php70: do not expose intArg

src/Php70/Php70.php

@@ -60,7 +60,7 @@ public static function error_clear_last()
         restore_error_handler();
     }
 
-    public static function intArg($value, $caller, $pos)
+    private static function intArg($value, $caller, $pos)
     {
         if (is_int($value)) {
             return $value;