Many changes to code structure are included:
- removed TIME_SLICE_IN_MS
- removed sychronized_indexed_list
- removed region_owned
- kernel_owned move to kernel.h, task_owned moved to task.h
- global configs moved to rust_globals.h
- changed #pragma once to standard guard in rust_upcall.h
- got rid of memory.h
getenv is not threadsafe and (maybe as a result) it's randomly crashing with
CFLAGS=-g and RUST_THREADS=32. Calls from rust code are still on their
own.
