Fix positioning of tabheader in order to be usable for scaling GUIs
WARNING: this changes position of current tabheaders, mods have to adjust!

sneaking

Also make a stray variable local.

Changes:
  * Add comments to explain the dumping code
  * Add support for dumping values of any type (as '<' <type> '>')
  * Add support for tables as keys in dump2()
  * Make dump2() return it's result (like dump()) rather than printing it
  * Simplify and optimize function serialization via serialize()

Fix doubleclick not working in singleplayer
Fix of by one issue on accessing raw list
Fix this->self
Fix copy&paste error for scroll button

Add TTL to item entities.

Fix crash on using cursor keys in client menu without selected server
Add support for non fixed size tabviews

Fix client not showing hearts and bubbles on connecting to old server
Fix server not remembering hud flags correctly

Add DPI support for statbar
Move heart+bubble bar to Lua HUD
Add statbar size (based upon an idea by blue42u)
Add support for customizing breath and statbar

This makes a number of changes:
  * Remove the dependency on marshal by using string.dump and loadstring.
  * Use lua_tolstring rather than having Lua functions pass string lengths to C++.
  * Move lua_api/l_async_events.* to cpp_api/s_async.*, where it belongs.
  * Make AsyncWorkerThread a child of ScriptApiBase, this removes some duplicate functionality.
  * Don't wait for async threads to shut down.  (Is this safe?  Might result in corruption if the thread is writing to a file.)
  * Pop more unused items from the stack
  * Code style fixes
  * Other misc changes

This reverts commit 5b518ed2.

This caused duplicate tracebacks and tracebacks when unwanted.
It also ignored the level argument to error() and didn't pass the message (or level) to debug.traceback().
Use xpcall() or lua_pcall()'s errorhandler argument instead.

since the object is not immediately removed, any other code may still
think an object is there, therefore leading to item duplication. This code
therefore sets the itemstring to '' after the object is picked up to avoid
such issues

Parallax mapping with slope information.
Overriding normal maps.