comment added to filesystem & file i/o code
fix fs_open() , now return error code correctly

originally ,it return -2 on error ,now return OPENFAIL (-1)
why it did that is unknown
also ,add indent here and there
delete function fio_getfd & put OPENFAIL in fio.c

fio_getfd() provide bound checking to opened file handle
,but is unused because fio_is_open_int() has already provided that.
also ,OPENFAIL is used to replace -1 literals.
fix missing break in stdin_read()
change filesystem.c from hash to name based search

to prepare for commend like "ls" , "cd"
change mkromfs.c to make standard romfs for file

work in progress on mkromfs.c
enable it to write the correct file header (not for directories yet)

for the format ,check :
https://www.kernel.org/doc/Documentation/filesystems/romfs.txt
mkromfs.c standard romfs for directories

romfs : https://www.kernel.org/doc/Documentation/filesystems/romfs.txt
debug for file part on mkromfs.c

padding for file added ,correction on size/padding calculation
fix writing out of bound bug in mkromfs.c

originally ,mkromfs writes out-of-bound value because variable 'b'
was mistaken as a 4-byte int rather then a byte.
fix : writing sections are now replaced by 2 new functions ,in which
size of variables are treated correctly.
add next_filehdr=0 if no next file & dir name

finalize mkromfs.c ,add in forgotten functions
modify romfs.c to use the new (standard) romfs format

the change is mainly done in adding romfs_get_file_by_name ,
which supports referencing file given a path. the file system no longer
uses hash.
a file size field is added to romfs_fds ,since new file header includes
file name ,which is variable length ,making directly referencing size
field from content pointer more difficult
fix dir spec.info in mkromfs & filesystem warning

when making directory in mkromfs ,forgot to add filename offset to
spec.info (points to files in directory)