It's looking like Glibc will add a renameat2 function
that is incompatible with Gnulib renameat2; see:
https://sourceware.org/ml/libc-alpha/2018-07/msg00064.html
To help avoid future confusion, rename renameat2 to something else.
Use the name 'renameatu', as the Gnulib function is close to the
Glibc function. Perhaps someday there will also be a renameat2
Gnulib module, which mimicks the future glibc renameat2, but that
can wait as nobody seems to need such a module now.
* lib/renameatu.c: Rename from lib/renameat2.c.
* lib/renameatu.h: Rename from lib/renameat2.h.
* modules/renameat2: Rename from modules/renameatu.
* modules/renameat2-tests: Rename from modules/renameat2-tests.
All uses of "renameat2" in identifiers or file name
changed to "renameatu", except for two instances in
lib/renameatu.c that deal with the Linux kernel's
renameat2 syscall.