review of nvm.nfs_mount_in_workspace src/unix/fs.cc rename_clobberingly

I've pushed nvm.nfs_mount_in_workspace. In src/unix/fs.cc, I've patched
rename_clobberingly to handle my use case of a subdirectory of a
workspace nfs mounted to a Lynx 5.0 disk.

Any comments?

I'm wondering if I should make the file protection mode wider than user
r/w. 

I tried leaving that param out, as the docs suggest it will use a
reasonable default depending on the environment, but that did _not_
work; I got random modes, including nobody read or write!

In any case, this works for my use case, and I'd be somewhat surprised
if anyone else ever needs it :).

-- 
-- Stephe