io.encodings.utf7: implementation of decoding for new codec utf7
io.encodings.utf7: better encoding using the group-by combinator
io.encodings.utf7: decoder implementation, doesn't support utf7imap4 yet
io.encodings.utf7: working utf7 decoding with tests
io.encodings.utf7: documentation and metadata files
io.encodings.utf7: cleaned up vocab per review

1. Tuple is used to hold the decoding buffer instead of a global
2. Fixed problematic sequence type conversions.
io.encodings.utf7: add copyright for Björn Lindqvist.
Initial commit of lookup-table AES implementation

In need of optimization and cleanup.  Uses 32-bit integers arithmetic
and seems to run very quickly (100k key expansions + encrypts in 3.88
= 400K/s encryption).  Based on p7zip's optimized C implementation.
crypto.aes: <sliced-groups> is now just <groups>, add a missing using.
unmaintained: fix <sliced-groups> to be <groups>.