Re-add P_ThingOnSpecial3DFloor for Lua backwards compatibility

See merge request !1905

UDMF: Use string values for the sector "triggerer" field

See merge request !1902

Disable exit sectors in non-NiGHTS special stages because they interfere with the pits

Closes #930

See merge request !1900

Revert Gamepads for now

See merge request !1926

Handle splitscreen lua hud lists separately

Closes #935

See merge request !1925

Invert OpenGL rollangle for papersprites to match software renderer behaviour

Closes #849

See merge request !1924

Minor interpolation fixes

Closes #900, #906, and #916

See merge request STJr/SRB2!1923

This reverts commit 696e2ab9, reversing
changes made to d98d5949.

This reverts commit 7f1cafcd, reversing
changes made to 696e2ab9.

This reverts commit 7d8e8e20, reversing
changes made to 7f1cafcd.

This reverts commit 6428d6fc.

This reverts commit ec58b150.

This reverts commit f5f22413.

This reverts commit df28ffd7.

This reverts commit fdb6f2af.

This reverts commit 71736f35, reversing
changes made to 4e3f7878.

This reverts commit 96bfd8ce, reversing
changes made to 24f9ec4e.

Fixes #935 by ensuring each drawlist is drawn separately while
stplyr is set correctly.

Fixes #900 pop-in animation being affected by framerate

Fixes #906

Uses the old displacement of the minecart to position the mark relative
to its destination. It's not completely correct, but it works.

Fixes #916

This reverts merge request !1920

Gamepad fixes & changes

Closes #813

See merge request !1899