Fix --remove-files.

Tar --remove-files relied on canonicalize_file_name,
which replaces symlinks in file name components with
the directories they point to. Due to this, tar
effectively ignored existence of symbolic links and
was unable to remove a directory that contained any
(Alexander Kozlov <akozlov@nada.kth.se>, 2010-03-15).

* gnulib.modules: Remove canonicalize.
* src/misc.c (normalize_filename): Rewrite
from scratch. The function operates only on
its input string, it makes no attempt to test
components for existence or to resolve symbolic
links.
* tests/Makefile.am (TESTSUITE_AT): Add remfiles03.at.
* tests/testsuite.at: Likewise.
* tests/remfiles03.at: New test case.
* NEWS: Update.