Set visibility on class properties of ReplacementArray

Set visibility on class properties of ReplacementArray

Usages in:

Core:
* HtmlFormatter: No referenced properties.
* Language: No referenced properties.
* LanguageConverter subclasses: I think there are no referenced properties
  here, but not 100% certain.
* Tidy: No referenced properties.

Extensions:
* AbuseFilter: No referenced properties.
* LiquidThreads: No referenced properties.
* Transliterator: No referenced properties.
* WYSIWIG: No referenced properties.

Change-Id: I1b2e3360468cbfc803ab884f999437e9b8c3758d