Fix scheduler starvation, use lists for scheduling

libmsl/m/system.h

@@ -19,6 +19,7 @@
 
 int quit (void);
 int test (char c);
+int sched (void);
 int map (int mem_rid, int vis, uintptr_t vaddr, uint32_t flags);
 int unmap (uintptr_t vaddr, size_t pages);
 int create_mem (int mem_rid, int vis, size_t pages);