Apply entab fix from Marko Kreen for these problems:

Apply entab fix from Marko Kreen for these problems:

- halt.c did not include stdlib.h, thus missed exit() prototype
- Makefile ignores BINDIR for install.
- Makefile calls install with user/group args, thus failing for regular user.

While trying it I noticed that the Makefile does not support VPATH builds ...