vr_rclone() shouldn't call brelse() for old_region.
Various build sys fixes

- there should be no manifest files in repo
- proper make clean targets
Header file and libc fixes

- Remove old hal stuff and moving it to a system wide location
- sigtimedwait() stub
- Add ARG_MAX to limits
- Various updates and stuff
Developing environ management

Store argv and env in a lightweight fashion by allocating a shared page
for argv and env data.

Change exec_file() to support new environ system.

This commit also adds a bunch of supporting functions and changes.