P-handler specific fix of bug 52762

* Till recently, the PHP parser treated empty lines with a single
  comment specially.  With a recent patch to the php parser, this
  special case has been removed and all "empty" lines (those with
  WS and comments-only only) are treated as transparent to the
  php parser.

* Parsoid had a special-case handling in the p-handler for
  single-comment empty lines to mimic the PHP parser. This patch
  removes the single-comment special case.

* The recently updated wt2html test is back to green now. Since
  parser test output changed, selser test run also changed.

  Updated blacklist to reflect changes.

Change-Id: I5299996bdfaaa8ec0e97faf8f3ab1fab1fa42eda
Merge "P-handler specific fix of bug 52762"