build: name temporary files in `Makefile.am' consistently.

build: name temporary files in `Makefile.am' consistently.

Sadly, we still have to jump through hoops for MICROS~1's very
old, very broken 8.3 naming convention, so we have to be careful
to be unique in the first 8 letters, and not to use two periods
in a filename, otherwise we could use the much more elegent
`temporary files use "$@T"' idiom:
* Makefile.am (libltdl/m4/ltversion.m4): Rename temporary file
to `ltversion.tmp'.
(libltdl/config/ltmain.sh): Rename temporary file to
`libltdl/config/ltmain.tmp'.
(libtoolize): Rename temporary file to `libtoolize.tmp'.
(tests/defs): Rename temporary file to `tests/defs.tmp'
(tests/testsuite): Rename temporary file to `tests/testsuite.tmp'.
(CLEANFILES): Append temporary files as we create rules that
use them.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>