(Bug 62647) Bug fix in separator handling of sol-transparent nodes

* My big separator cleanup/refactoring patch added checks for
  not updating constraints when sol-transparent nodes (from original
  wikitext) were encountered. However, that check was buggy in that
  it only checked whether one of the two nodes came from original
  wikitext instead of checking whether *both* came from original
  wikitext.

  This, in effect, introduced the errors reported in bug 62647

* This patch fixes the bug and also adds a new parser test that
  documents this behavior.

Change-Id: Iee7557017f30e3acd61c0b075bfff857b363e792
Merge "(Bug 62647) Bug fix in separator handling of sol-transparent nodes"