[PATCHES] struct path constification

[Al Viro]

	This is mostly whack-a-mole stuff - a bunch of places
are passing struct path pointers around, without bothering
to mark them const, even though they are not going to try
and modify the contents of struct path.

	It's a bad practice, since there are invariants along
the lines of "file->f_path stays unchanged open-to-release"
and verifying those can get very unpleasant when you are
forced to take detours down the long call chains that could've
been avoided.

	Patches in that pile are independent from each other
and if anyone wants to grab some of them into subsystem's
tree - just say so; I'll be happy to exclude those from the
vfs.git branch if they go into another tree.

	Currently they are in vfs.git#work.path; individual
patches in followups.