[PATCH 2/5] Import idx.h from gnulib

[Paul Eggert]

Thanks, this looks good. Also, the following "[PATCH 3/5] Import 
filename.h from gnulib" looks good. I merged both changes into Gnulib here:

http://git.savannah.gnu.org/cgit/gnulib.git/commit/?id=1013adf6bf48627f84a9043cf2631ff13d2a452f