php: 5.6 -> 7.0

I'll probably regret this in testing period, but let's bump php
since 5.6 support expires in December.

Changed files
+2 -2
pkgs
top-level
+2 -2
pkgs/top-level/all-packages.nix
···
inherit (callPackages ../development/interpreters/perl {}) perl perl520 perl522;
-
php = php56;
+
php = php70;
-
phpPackages = php56Packages;
+
phpPackages = php70Packages;
php56Packages = recurseIntoAttrs (callPackage ./php-packages.nix {
php = php56;