sheepfs: fix complie error when http isn't enabled

Forgot to remove -lcurl in my last patch, remove it.

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
sheep: fix some compile errors

Both MIN/MAX and roundup are provided by glibc and would cause compile error
when we #include <sys/param.h>. Just use GNU version.

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep: introduce NFSv3 transport

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep/nfs: add mount protocol stub

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
dog: add nfs command

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
util: add PTR_ERR helpers

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep/nfs: add basic file system framework

Add basic inode, dentry structures and just support 'ls' /mntpoint operation.

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep: clean up sd_inode btree error code

These error codes are used internally, not for client communication.

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep/nfs: support lookup/create/setattr nfs operation

Now we support 'touch' command.

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep/nfs: implement read/write nfs operation

Now we support more bash command such as cp, mv, echo, cat ...

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep/nfs: add mkdir support

Now we support 'mkdir' command and gain hierarchical structure support.

TODO:
 - make dentry operation operate on top of 'file' operation
 - add hash or btree based dentries management

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep: make stat_data_objs a generic function

and rename it as sd_inode_stat()

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep/nfs: implement nfs3_fsstat operation

Now we support 'df' command to get file system stats.

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep/nfs: implement link/symlink operation

Signed-off-by: Liu Yuan <namei.unix@gmail.com>