Use vmalloc for ppp_deflate workspace. It's 400KiB, and kmalloc strangely
    doesn't seem to work very well for that :)
    
    Use schedule_task to do a delayed cleanup, because the z_comp_free routine
    is called with spinlocks held, hence we can't just call vfree().
    
    Fix double MOD_DEC_USE_COUNT when allocation fails, for both compression
    and decompression workspaces.
    
    Change licence text to one that insmod likes.