Split gui_scaling to gui_scaling + hud_scaling as those elements need different handling on some devices

Switch default scaling factor to 0.75 as most ppl seem to have 96dpi screens instead of previous assumed 72

If liquid_queue_purge_time == 0 then disable the queue size limiting and make this the default setting
Additionally, liquid_loop_max now defaults to 100000

Fix non coding style conforming glb_fontengine to g_fontengine
Fix fonts never been deleted due to grabbed to often

Signed-off-by: Craig Robbins <kde.psych@gmail.com>

Signed-off-by: Craig Robbins <kde.psych@gmail.com>

Since minetest has no mobs within the core anymore, I suppose these
settings and code should go. Any mod that uses `minetest.setting_getbool`
will work with no problem since the default return value is `false`.

This can delay connections by several minutes.

There have been plenty of ppl involved in creating this version.
I don't wanna mention names as I'm sure I'd forget someone so I
just tell where help has been done:
- The partial android versions done by various ppl
- Testing on different android devices
- reviewing code (especially the in core changes)
- testing controls
- reviewing texts

A big thank you to everyone helping this to be completed!

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

Add (experimental) support for topbottom as well as sidebyside 3d mode

Minor coding style fixes

Add support for (configurable) multiline hotbar
Improved screensize handling
Add userdefined gui scale by BlockMen

Parallax mapping with slope information.
Overriding normal maps.

Remove flagmask field from set_mapgen_params table
Add small bits of needed documentation

Add checks for invalid user input for important settings
Rename Settings::tryGet* to Settings::get*NoEx for consistency

MapgenParams is no longer a polymorphic class, eliminating the need for messy and bug-prone reallocations.
Separation between the common and mapgen-specific parameters is now strongly defined.
Mapgen parameters objects are now properly encapsulated within the proper subsystems.