Update libarchive to 3.2.0

New features:
- new bsdcat command-line utility
- LZ4 compression (in src only via external utility from ports)
- Warc format support
- 'Raw' format writer
- Zip: Support archives >4GB, entries >4GB
- Zip: Support encrypting and decrypting entries
- Zip: Support experimental streaming extension
- Identify encrypted entries in several formats
- New --clear-nochange-flags option to bsdtar tries to remove noschg and
  similar flags before deleting files
- New --ignore-zeros option to bsdtar to handle concatenated tar archives
- Use multi-threaded LZMA decompression if liblzma supports it
- Expose version info for libraries used by libarchive

Patched files (fixed compiler warnings):

contrib/libarchive/cat/bsdcat.c (vendor PR #702)
contrib/libarchive/cat/bsdcat.h (vendor PR #702)
contrib/libarchive/libarchive/archive_read_support_format_mtree.c (PR #701)
contrib/libarchive/libarchive_fe/err.c (vendor PR #703)

MFC after:	1 month
Relnotes:	yes