gcc_release (build_tarfile): Build .bz2 files instead of .gz files.
* gcc_release (build_tarfile): Build .bz2 files instead of .gz files.
(build_bz2): Rename to build_gzip and create .gz files from .bz2
files instead of the other way around.
(build_gzip): New function.
(build_diffs): Build .bz2 files instead of .gz files.
(build_diff): Use .bz2 files instead of .gz files.
Make an error message independent of the compression format.
(MODE_BZIP2): Rename to MODE_GZIP. Related changes to the
invocation of this script.
(MODE_GZIP): New variable.
(OLD_TARS): Use .bz2 archive of the previous snapshot.