Add tests for archive_write_set_format_by_name.
Add tests for archive_write_add_filter_by_name.
Fix build failure without zlib.
Fix test failure without zlib.
Fix memory overflow.
Fix test failure without liblzma.
Fix issue 293; plug memory leaks.
Style: Whitespace around '='
Fix test_read_append_filter_program

canGzip() tests for "gzip -d" then try to use gunzip.
On some systems, gzip is available while gunzip is not.
Use gzip -d as this is what we are looking for
Merge pull request #31 from bamiaux/fix_gunzip_test

Fix test_read_append_filter_program
Remove comment and fix failure message to indicate gzip is expected.