[Command] Added LockHelper

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes https://github.com/symfony/symfony/pull/10475
| Applies to    | Symfony version 2.6+
| Fixed tickets | -
Regarding this phrase:

```
This mechanism was introduced back in 1963 for the mainframes.
```

It was used in the blog post to provide some fun fact, but I think that it's a bit out of context for the Symfony documentation. Moreover, in the blog post we showed a link to the Wikipedia article mentioning this fact.

I propose to remove that phrase or reword it to make it less specific:

```
This mechanism was introduced a few decades ago for mainframes, but continues being useful for modern applications.
```