* lib/splitstring.c: New file; defines splitstring(), which will
non-destructively locate character-separated fields in a string.
* lib/splitstring.h: New file; declares splitstring.
* lib/test_splitstring.c: New file; unit test for splitstring.c.
* lib/nextelem.c: Delete (obsoleted by splitstring.c).
* lib/nextelem.h: Delete (obsoleted by splitstring.h).
* lib/Makefile.am (libfind_a_SOURCES): Add splitstring.c,
splitstring.c. Remove nextelem.c, nextelem.h.
(check_PROGRAMS): Add test_splitstring.
(TESTS): Add test_splitstring.
(test_splitstring_SOURCES): Sources for the
test_splitstring unit test.
* locate/locate.c: Include splitstring.h rather than nextelem.h.
(dolocate): Use splitstring rather than next_element. In places
where we need a nul-terminated string, use strndup() to create it.
Convert some space-tab sequences to regular spacing.
* find/parser.c: Include splitstring.h rather than nextelem.h.
(check_path_safety): Use splitstring rather than next_element.
* import-gnulib.config (modules): Depend on the module strndup.
* cfg.mk: Exempt lib/test_splitstring.c from calling
bindtextdomain or set_program_name.
