Fix lib/replace

Fix lib/replace

Warnings are generated when compiling strptime.c.  Why is it being
compiled on Linux?  strptime(3) has been in glibc for 15 years!

It turns out that some of the test fragments were being looked for in
lib/replace/test/ and some in lib/replace/tests/.  In addition,
test*/strptime.c was missing.

Move the tests to lib/replace/test/ for consistency with upstream
(Samba) and copy in test/strptime.c from Samba.  Tweak repdir.m4 to
handle the directory rename.

Signed-off-by: Martin Schwenke <martin@meltin.net>
(This used to be ctdb commit aaf1ddfc83cf2ede29288baf04a1aa1c69a5cab5)