[3.3] Rewrite parser and fix escaped quotes in multiline values - #322

This commit added symfony/polyfill-ctype to composer.json instead php[ctype].
I can't see the rational of this choice. (And I'd rather before off this extra-dependency)

This adds the dependency because we are using the ctype functions.

The symfony/polyfill-ctype package has ext-ctype as a recommended package. When you install phpdotenv and you don't have the php extension, composer will actually warn you about this, and recommend you install it.

... but if one has php[ctype] it installs an unneeded dependency.

You can stop this happening in your app with the following trick. In your app's composer.json, do this:

{
    ...
    "replace": {
        "symfony/polyfill-ctype": "*"
    },
    "require": {
        ...
        "ext-ctype": "*",
        ...
        "vlucas/phpdotenv": "^3.3"
    },
    ...
}