Codechange: Remove direct access to _colour_gradient.

Access is now through GetColourGradient, which ensures parameters are in range.

Codechange: allow certain enumeration to be added

Otherwise C++20 doesn't like it.

Codechange: automatic adding of _t to (u)int types, and WChar to char32_t

for i in `find src -type f|grep -v 3rdparty/fmt|grep -v 3rdparty/catch2|grep -v 3rdparty/opengl|grep -v stdafx.h`; do sed 's/uint16& /uint16 \&/g;s/int8\([ >*),;[]\)/int8_t\1/g;s/int16\([ >*),;[]\)/int16_t\1/g;s/int32\([ >*),;[]\)/int32_t\1/g;s/int64\([ >*),;[]\)/int64_t\1/g;s/ uint32(/ uint32_t(/g;s/_uint8_t/_uint8/;s/Uint8_t/Uint8/;s/ft_int64_t/ft_int64/g;s/uint64$/uint64_t/;s/WChar/char32_t/g;s/char32_t char32_t/char32_t WChar/' -i $i; done

Codechange: remove queue_wrap / last_position from mouse movement

No backend uses it anymore, so also no longer any need to support
it.

Cleanup: Remove obsolete (Make)EnumPropsT. (#10697)

This was used by the command system to help extract p1/p2 parameters, which no longer happens.

Codechange: Make SpriteType, CargoSortType, SourceType and ScriptType enum classes. (#10663)

This avoids a (soft) namespace conflict between the four ST_* enums.

Change: Make tick length 27 milliseconds (#10607)

This makes a month last about 60 seconds, allowing the use of real-time units in game.

Co-authored-by: Niels Martin Hansen <nielsm@indvikleren.dk>

Add: [Emscripten] use "relative mouse mode" with SDL2

This mode doesn't wrap the mouse constantly, but requests SDL
to lock the mouse pointer. This is needed, as with Emscripten
you are not allowed to change the mouse poisition (only to lock
it into place).

Add: support for emscripten (play-OpenTTD-in-the-browser)

Emscripten compiles to WASM, which can be loaded via
HTML / JavaScript. This allows you to play OpenTTD inside a
browser.

Co-authored-by: milek7 <me@milek7.pl>

Feature: Group liveries, and livery window usability enhancements. (#7108)

* Change: Replace checkbox in livery selection window with Default option in drop down selection.

This reduces clutter in the UI and allows for primary/secondary colours to independently follow the default scheme if desired.

* Feature: Add vehicle group liveries.

(svn r26522) -Add: A config-file-only setting to disable usage of 8bpp video modes.
-Remove: [win32] fullscreen_bpp setting, which is replaced by above setting.
-Change: Disable usage of 8bpp blitters and video modes by default. Many modern OS and hardware cause issues with those.

(svn r22419) -Change: Always use the DOS palette for drawing.
-Remove: the '-i' option for palette selection.

(svn r13639) -Codechange: rewrite 32bpp-anim and 32bpp-optimized drawing and encoding so it uses similiar scheme as 8bpp-optimized
All zoom levels are stored and a kind of RLE is used. Together with further changes and reducing number of variables, drawing is ~50% faster in average.