Do not include default column limit in schema.rb

Follow up of #20815.

```ruby
class CreatePeople < ActiveRecord::Migration[5.0]
  def change
    create_table :people do |t|
      t.integer :int
      t.bigint :bint
      t.text :txt
      t.binary :bin
    end
  end
end
```

Result.

In postgresql and sqlite3 adapters:

```ruby
ActiveRecord::Schema.define(version: 20160531141018) do

  create_table "people", force: :cascade do |t|
    t.integer "int"
    t.bigint  "bint"
    t.text    "txt"
    t.binary  "bin"
  end

end
```

In mysql2 adapter:

```ruby
ActiveRecord::Schema.define(version: 20160531141018) do

  create_table "people", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4" do |t|
    t.integer "int"
    t.bigint  "bint"
    t.text    "txt",  limit: 65535
    t.binary  "bin",  limit: 65535
  end

end
```

After this patch:

```ruby
ActiveRecord::Schema.define(version: 20160531141018) do

  create_table "people", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4" do |t|
    t.integer "int"
    t.bigint  "bint"
    t.text    "txt"
    t.binary  "bin"
  end

end
```

1 files changed, 2 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 44b4b547f3..718a6c5b91 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -41,14 +41,14 @@ module ActiveRecord
       NATIVE_DATABASE_TYPES = {
         primary_key: "int auto_increment PRIMARY KEY",
         string:      { name: "varchar", limit: 255 },
-        text:        { name: "text" },
+        text:        { name: "text", limit: 65535 },
         integer:     { name: "int", limit: 4 },
         float:       { name: "float" },
         decimal:     { name: "decimal" },
         datetime:    { name: "datetime" },
         time:        { name: "time" },
         date:        { name: "date" },
-        binary:      { name: "blob" },
+        binary:      { name: "blob", limit: 65535 },
         boolean:     { name: "tinyint", limit: 1 },
         json:        { name: "json" },
       }