Backport more skyeye fixes from 3dmoo

armemu: Fix SSUB16

Kernel: Add missing permissions

FS_U: Implemented the SaveData archive

The savedata for each game is stored in /savedata/<ProgramID> for NCCH files. ELF files and 3DSX files use the folder 0 because they have no ID information

Got rid of the code duplication in File and Directory

Files that deal with the host machine's file system now live in DiskFile, similarly for directories and DiskDirectory and archives with DiskArchive.

FS_U: Use the correct error code when a file wasn't found

Broken from the same reason SADD16 was.

The lo part of the result should only be constructed from the lo halfwords of rm and rn.
The hi part of the result should only be constructed from the hi halfwords of rm and rn.

armemu: Fix SADD16

armemu: Join QADD16/QSUB16 and fix saturation clamping.

The lo and hi parts of the result were being constructed as a result of hi and lo halfword intermixing from the rm and rn regs. However the lo part of the result should be constructed only from the lo halfwords of rm and rn, and the hi part of the result should only be constructed from the hi halfwords of rm and rn.

Join SMUAD, SMUSD, and SMLAD ops. Also fix them as well.

armemu: Backport some VFP fixes from 3dmoo.

Wrong values were being multiplied together.

The only difference between these ops is one adds and one subtracts. Everything is literally the same.

Comment out empty arrays causing compile errors in MSVC

armemu: Implement UXTAB16

Archive refactor

- Refactor FS::Archive internals to make Archive creation and lifetime
  management clearer.
- Remove the "Archive as a File" hack.
- Implement 64-bit Archive handles.

Fix spelling mistakes.