Pulled from 4.x branch, see #1894.

Prettier v2 has the following breaking changes:
* enforces spaces between `function` and params
* enforces trailing commas by default

This is needed in order to use `globalThis`, see #1894.
It also made it possible to remove some old polyfills and fallbacks.

Fixes #1820
Closes #1821

Related to c295ef0.

Closes #1696

This was found by running an IntellijIDE
code inspection for proofreading.

If `global` is used and handlebars is compiled for browser
usage without a Node.js `global` polyfill, handlebars
fails with a `global is undefined` error.

Fixes #1593

# Conflicts:
#	components/bower.json
#	components/handlebars.js.nuspec
#	components/package.json
#	integration-testing/multi-nodejs-test/test.sh
#	package-lock.json
#	package.json

Extracts the parser to `@handlebars/parser`, where it can be shared
between different implementations. This means that e.g. Glimmer/Ember
will be able to iterate on new features without forcing Handlebars to
adopt them immediately, and vice versa. All implementors will be able to
absorb changes as it makes sense for them.

There is a small typo in lib/handlebars/compiler/whitespace-control.js.

Should read `multiple` rather than `mulitple`.

# Conflicts:
#	components/bower.json
#	components/handlebars.js.nuspec
#	components/package.json
#	package.json

# Conflicts:
#	components/bower.json
#	components/handlebars.js.nuspec
#	components/package.json
#	package.json

- helpers should always be a function, but in #1639 one seems to
  be undefined. This was not a problem before 4.6 because helpers
  weren't wrapped then.
  Now, we must take care only to wrap helpers (when adding
  the "lookupProperty" function to the options), if they
  are really functions.

- fix link url to handlebarsjs.com

... to be graceful with older browser without "console"

This commmit adds the runtime options
- `allowProtoPropertiesByDefault` (boolean, default: false) and
- `allowProtoMethodsByDefault` (boolean, default: false)`
which can be used to allow access to prototype properties and
functions in general.

Specific properties and methods can still be disabled from access
via `allowedProtoProperties` and `allowedProtoMethods` by
setting the corresponding values to false.

The methods `constructor`, `__defineGetter__`, `__defineSetter__`, `__lookupGetter__`
and the property `__proto__` will be disabled, even if the allow...ByDefault-options
are set to true. In order to allow access to those properties and methods, they have
to be explicitly set to true in the 'allowedProto...'-options.

A warning is logged when the a proto-access it attempted and denied
by default (i.e. if no option is set by the user to make the access
decision explicit)

# Conflicts:
#	components/bower.json
#	components/handlebars.js.nuspec
#	components/package.json
#	package.json

Disallow access to prototype properties and methods by default.
Access to properties is always checked via
`Object.prototype.hasOwnProperty.call(parent, propertyName)`.

New runtime options:
- **allowedProtoMethods**: a string-to-boolean map of property-names that are allowed if they are methods of the parent object.
- **allowedProtoProperties**: a string-to-boolean map of property-names that are allowed if they are properties but not methods of the parent object.

```js
const template = handlebars.compile('{{aString.trim}}')
const result = template({ aString: '  abc  ' })
// result is empty, because trim is defined at String prototype
```

```js
const template = handlebars.compile('{{aString.trim}}')
const result = template({ aString: '  abc  ' }, {
  allowedProtoMethods: {
    trim: true
  }
})
// result = 'abc'
```

Implementation details: The method now "container.lookupProperty"
handles the prototype-checks and the white-lists. It is used in
- JavaScriptCompiler#nameLookup
- The "lookup"-helper (passed to all helpers as "options.lookupProperty")
- The "lookup" function at the container, which is used for recursive lookups in "compat" mode

Compatibility:
- **Old precompiled templates work with new runtimes**: The "options.lookupPropery"-function is passed to the helper by a wrapper, not by the compiled templated.
- **New templates work with old runtimes**: The template contains a function that is used as fallback if the "lookupProperty"-function cannot be found at the container. However, the runtime-options "allowedProtoProperties" and "allowedProtoMethods" only work with the newest runtime.

BREAKING CHANGE:
- access to prototype properties is forbidden completely by default