7zz: compile optimized assembly code for x86_64
7zz: compile optimized assembly code for x86_64

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
```

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