[5.6] Quote collation name in MySQL migrations

[staudenmeir]

Creating a column with a binary collation fails in MySQL:

Schema::create('table', function ($blueprint) {
    $blueprint->string('column')->collation('binary');
});

This executes the following SQL:

create table `table` (`column` varchar(255) collate binary not null)
    default character set utf8mb4 collate utf8mb4_unicode_ci

The query fails: Syntax error [...] the right syntax to use near 'binary not null) [...]

It works after quoting the collation name:

create table `table` (`column` varchar(255) collate 'binary' not null)
    default character set utf8mb4 collate 'utf8mb4_unicode_ci'

Fixes #23944.