Fixes STJr/SRB2#865

Also clean up redundant "startingspheres" variable

Fixes #71

- Added A_SetShadowScale
- Added A_ShadowScream which combines the above with A_Scream, used for 
badnik explosions
- Gave flickies drop shadows

Turn the console warning into a devmode print because turns out it happens more often than I thought

Some code assumes that P_SpawnMobj can never return NULL
So spawn MT_RAY in it's place when attempting to spawn MT_NULL and show a console warning

This reverts commit b2d693a5.

So they don't mess with shell scripts that expect SRB2 to exit when it crashes (like most other programs)