Allow equal and tilde chars in wikilink targets

This fixes link parsing and -roundtripping on [[ja:岩波版聖書]].

Simple test cases:
[[Special:Booksources/isbn=4-00-026157-6]]
[[Foo~bar]]

Change-Id: I6b87013fccec2ff1d524f853684f5f4c1d8d5a17
Merge "Allow equal and tilde chars in wikilink targets"