Importing usr.bin/split

Replaces commands/split. No Minix-specific changes needed.

Change-Id: I3c6551cf52d4c43eea0e8005b9cae83e17271f2d
Importing usr.bin/csplit

No Minix-specific changes needed.

Change-Id: Id5d5deb380208ba9fccf404eab5128f8d892c255
Importing usr.bin/fsplit

No Minix-specific changes needed.

Change-Id: I78021e6485b40a5b9f98b5d0e5ce0dc82b1ae46a