Add a lot of stuff scraped from *i's version of the code, plus a couple of additional bits.

Adapted from *i:
- Show a confirm dialog when interrupting a special node sequence
- New monster special ability: call global special node (as an action, not on death)
- New item special ability: call global special node
- Check there's a monster death special before calling it (wasn't necessary before, might be now with the special queue changes)
- Queue specials that are triggered while another special is in progress, instead of ignoring them; they will be run after the current special in progress finishes.
- *i's version of petrification touch is currently active only for monster-on-monster combat; need to merge with my version for monster-on-pc combat.
- Pass party location to special in use special item context
- Fix set town visibility node (was checking wrong field and thus could not hide towns)
Special nodes:
- Town Hostile: change to Set Town Attitude
- Select PC node: option to select random PC
- Affect special nodes can now affect monsters
- Fix affect death node reviving non-existent PCs
- Affect Spells: Can remove spells, and can affect level 1-3 spells
- If Objects: Merged from If Barrels and If Crates
- If Species: Replaces If Cave Lore
- If Trait: Replaces If Woodsman
- If Statistic: Replaces If Enough Mage Lore
- Change Lighting: Can affect town's global lighting setting, player's light level, or both at once.
- Pointers! Actually, I'd already implemented the callbacks for setting and getting them, but they're now actually used, and the implementation has been tweaked a little.
- Campaign flags! Again, I'd already implemented them sorta, but I tweaked things and they ended up sort of halfway between the two implementations. Plus there's now a special node to set them.

Additional bits:
- Special queue now uses an std::queue instead of a basic array.
- Enum for town lighting levels
- Disease touch ability is now honoured for monster-on-monster combat
- See monster special context now passes the monster's location as the trigger location; also, removed the double-trigger from one circumstance.
- Along with the set town attitude change, there's now the possibility for making the town hostile to trigger a special node, which can cause the party to be slain.
- Select PC special node: option to select specific PC
- Spell IDs for use in shops and Affect Spell nodes have changed so that 0 is now the first level 1 spell, and so forth.
- add_string_to_buf can now auto-split the string over multiple lines, and the special node that uses it takes advantage of this
- Special node parser warns if a node type is missing a corresponding opcode
- Reserved "pointers" to access the special node's trigger location (this was *i's idea, but he never implemented it)

osx/boe.town.h

@@ -6,7 +6,7 @@ void start_town_mode(short which_town, short entry_dir);
 void terrain_under_rentar();
 location end_town_mode(short switching_level,location destination);  // returns new party location
 void handle_leave_town_specials(short town_number, short which_spec,location start_loc) ;
-void handle_town_specials(short town_number, short entry_dir,location start_loc) ;
+void handle_town_specials(short town_number, bool town_dead,location start_loc) ;
 bool abil_exists(short abil) ;
 
 void start_town_combat(short direction);