Update Makefile and header files

* Don’t use __DEBUG__ - it caused seg-faults!
* Use #def for PROC instead
Update documentation
Use new #def add new function

* New functio to remove directories
* Use #def for proc fs info
Use #defs for mkfs
Use #def's where appropriate, empty buffers before use
Add dry run option to mkstegfs
Forget password on close, remember on open