disable wikitext processing in history content snippets

Some html from parsoid was being striped down to plaintext, but due
to the usage of Message::parse for history descriptions it was
being parsed as wikitext.

Patch explicitly escapes content for html output and marks it as so.

Bug: 67546
Change-Id: Ib75eac5335d9094dc3fd4363e200d2be8e43169e
Merge "disable wikitext processing in history content snippets"