Revert binary database block position encoding

This reverts commits a2003b0d553c7223a61c75e5dad79ea68e058ba2 and 54ffe2e5de9ce44129f84f4748743f893b75fda7.

These weren't correct.  Add a black magic warning instead.
Fix argument type of the RaiseException() function
Fix lost pause support in singleplayer
Revert "Add backtrace to error function"

This reverts commit 5b518ed2feff28c9bf21ad940c1b211b72d71bd1.

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.
Update documentation on is_ground_content
Fix directional fog color in front view
Remove useless MSVC project files
Move the old stuff to doc
Client: Don't crash if trying to draw too many items from inventory in HUD
Add support for dpi based HUD scaling
Add support for (configurable) multiline hotbar
Improved screensize handling
Add userdefined gui scale by BlockMen
Only push the Lua error handler once
Remove dependency on marshal and many other async changes

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
Fix code style of async API
Add support for function serialization to minetest.serialize
Fix rounding issue of hud dpi on some machines
Make debug text adjust it's border to the screensize and fix a border update bug
Add download rate to media progress bar (non http mode only!)
Minor coding style fixes
Add proper lua api deprecated handling
Fix usage of deprecated functions in builtin
Add hack to avoid 2s startup delay on local games