Revert breaking PatternSynonyms changes

This reverts XHtml changes of commit
7c905816eb12981840efe4136989799db437f357.

This commit broke tests in at least two ways:

* added spurious whitespace to the front of each function name (not user
  visible)

* made all infix data types now be parenthesised (very user visible)

While the first one is easily fixable, I don't know about the second
one. I dare not try because the commit in question added no tests about
the added feature so it's impossible to tell what we're breaking.

We can not simply revert the full commit due to GHC API changes for
which it accounts for. We simply revert the changes to XHtml backend.