Eliminate non-existent index notices

Adds an isset($this->cchunk["appendlater"]) check to lines 425 and 433 to eliminate non-existent index notices.
- fixed bug PhD generates garbled chm on PHP 5.4.0 or later.
move generating dt tags from varlistentry to term
Merge pull request #1 from TheFrozenFire/patch-1

Eliminate non-existent index notices

* TheFrozenFire/patch-1:
  Eliminate non-existent index notices
Merge pull request #3 from mumumu/fix_garbled_chm_on_php5_4_0_or_later

PhD generates garbled chm on PHP 5.4.0 or later.

* mumumu/fix_garbled_chm_on_php5_4_0_or_later:
  - fixed bug PhD generates garbled chm on PHP 5.4.0 or later.
Merge pull request #4 from salathe/salathe/66316-dtdd

Move generating dt tags from varlistentry to term

* salathe/salathe/66316-dtdd:
  move generating dt tags from varlistentry to term