New STJR Intro and related changes (resolves #202)

The PURE FAT Intro was introduced over 5 years ago when SRB2 2.1.0 was released, as an attempt to make the game sound less serious. However it was not liked by many for various of reasons, and that's where this branch comes in, it replaces the PURE FAT Intro with a new STJR Intro, gfx provided by @SeventhSentinel.

A disclaimer stating the should not be sold is shown on startup now, as part of the new intro.

In order to company this change, a new lump named STARTUP was introduced, leaving CONSBACK reserved for the actual console.

Software mode gif:

OpenGL mode gif:

newintro.zip Zip file containing the EXE plus stuff needed for it. (Updated 29/8/2020 - New build and tweaked jingle with shorter fade out)