elist: Fix elist_splice() function
error: Rename log() to log_msg()

There is already a log() function in the C library...
game: Add minimum delay for asteroid creation
game: Make sure asteroids are created inside the clipping area
game: Fix memory corruption when deleting hit asteroids

When an asteroid was hit by more than one missile, it was deleted
multiple times (once for each hit).
game: Update score when player destroys an asteroid
game: Create fragments when a missile hits an asteroid