* _7zz: correct license and remove p7zip dependency
The code under Compress/Rar* is licensed under a specific unRAR license
Also Compress/LzfseDecoder.cpp is covered by BSD3
The unRAR code is removed from the `.tar.xz` since the license posits you
agree or remove the code from your hard drive
This adds some complexity to updating 7zz so there is also an update
script
Meta has been updated and tweaked
Source is now downloaded from sourceforge in the `.tar.xz` version to
avoid depending on p7zip
* _7zz: add notice of the license updates and optional unRAR licenced code
Use uasm to compile the optimized code instead of generic C code for
faster operations.
Before:
```
7zz x 10.83s user 0.40s system 98% cpu 11.439 total
```
After:
```
7zz x 6.87s user 0.40s system 98% cpu 7.395 total
```
* 7zz: 21.01 -> 21.04
Also build from source instead of using the binaries.
We cannot (yet) build the fully optimized version as it requires the
ASMC assembler which currently doesn't build with GCC.
