This is probably the largest chunk in quota patches. It removes old quotactl interface
and implements new one. New interface should not need arch specific conversions so they
are removed. All quota interface stuff is moved to quota.c so we can
easily separate things which should be compiled even if quota is disabled (mainly
because XFS needs some interface even if standard VFS quota is disabled).
Callbacks to filesystem on quota_on() and quota_off() are implemented (needed by Ext3),
quota operations callbacks are now set in super.c on superblock initialization and
not on quota_on(). This way it starts to make sense to have callbacks on alloc_space(),
alloc_inode() etc. as filesystem can override them on read_super(). This will be used
later for implementing journalled quota.