Use portable functions for reading/writing sector effect thinker
structures.

Subversion-branch: /branches/v2-branch
Subversion-revision: 2685
Map thing type and state table indexes to those used by Vanilla Heretic
v1.3, for savegame compatibility.

Subversion-branch: /branches/v2-branch
Subversion-revision: 2686
Fix comments: HHE, not Dehacked.

Subversion-branch: /branches/v2-branch
Subversion-revision: 2687
Translate HHE thing numbers according to patch exe version number, as
our mobjinfo table contains an extra entry.

Subversion-branch: /branches/v2-branch
Subversion-revision: 2688