Fix bugs in handling the --remove-files option.

Fix bugs in handling the --remove-files option.

Make sure the files are deleted only if they were succesfully stored
to the archive.

* src/exit.c: New file.
* src/unlink.c: New file.
* src/Makefile.am (tar_SOURCES): Add exit.c and unlink.c.
* src/common.h: Include progname.h
(program_name): Remove global.
(records_written): New extern.
(queue_deferred_unlink, finish_deferred_unlinks): New prototypes.
(fatal_exit_hook): New extern.
* src/create.c (create_archive): Call finish_deferred_unlinks.
(dump_hard_link, dump_file0): Don't actually unlink the file,
queue it to deferred_unlinks instead.
* src/delete.c (records_written): Remove extern: declared in
common.h.
* src/extract.c (extract_archive): Set fatal_exit_hook.
(fatal_exit, xalloc_die): Move to exit.c
* src/system.c (sys_wait_for_child): Exit immediately
if the child dies or exits with a non-zero status.
(sys_child_open_for_compress)
(sys_child_open_for_uncompress): Use set_program_name,
instead of setting program_name directly.
* src/tar.c (main): Use set_program_name,
instead of setting program_name directly.

* tests/Makefile.am (TESTSUITE_AT): Add remfiles01.at
and remfiles02.at.
* tests/testsuite.at: Likewise.
* tests/gzip.at: Reflect the above changes.