Kernel Memory Allocator

A new kernel memory allocator (kernel malloc) was added to Digital UNIX to use kernel-wired memory more efficiently. All calls to the mbuf allocator are now mapped to the new kernel memory allocator. In addition, several components of the I/O subsystems can use the kernel memory allocator directly, rather than having to manage memory on their own. As a result, we save the amount of memory these allocators were reserving. In addition, the new allocator handles allocation under interrupt context better than the kalloc allocator and has a garbage collection thread to free memory.