add some comments, minor cleanups

make read_file global

fs support is not optional

make fs menuconfig

make fs support mandatory

add erase function

add erase

use dev_read/dev_write

- do more POSIX:
  - use DIR instead of struct dirent
  - use (struct dirent)->d_name instead of (struct dirent)->name
- switch to a new layout for U_BOOT_CMD:
  - use C99 initializers to be able to add more fields to the
    command struct
  - add aliases for commands (needed mainly for help -> ? and test -> [
  - This is not done for all commands yet, but the compiler will tell you ;)

let normalise path allocate the string instead of changing the original one

fix truncate (again). This still looks ugly

fix truncate

fix mem hole

include asm-generic in errno.h instead of all other files

- fix free corruption in open
- simplify mount()
- fix mem hole

add rmdir and unlink, make creat more like posix, add common function for prerequites checking

implement . and .. entries

use xzalloc instead of malloc/memset

remove handling of / in stat function. We will never be called with / here

add lseek implementation, remove special handling of /dev/ (is now implemented as devfs)

add devfs

read support for ramfs

more FS work