Add AIX support

[librepower]

Add AIX support

Summary

This PR adds support for IBM AIX operating system.

Changes

• filesystems_aix.go: AIX-specific filesystem type detection
• mounts_aix.go: Mount point enumeration using AIX's mount command and statfs syscall

Implementation Notes

AIX doesn't have /proc/self/mountinfo like Linux or Getfsstat like BSD, so the implementation parses the output of the mount command and uses unix.Statfs for filesystem statistics.

Filesystem Types

• Network: nfs, nfs3, nfs4, cifs, smbfs, afs
• Special: procfs, namefs, sfs, cdrom
• FUSE: Not supported on AIX (returns false)

Testing

Tested on AIX 7.3 TL4 (POWER9):

$ ./duf
╭──────────────────────────────────────────────────────────────────────────────╮
│ 9 local devices                                                              │
├──────────────────┬────────┬────────┬────────┬────────┬───────┬───────────────┤
│ MOUNTED ON       │   SIZE │   USED │  AVAIL │  USE%  │ TYPE  │ FILESYSTEM    │
├──────────────────┼────────┼────────┼────────┼────────┼───────┼───────────────┤
│ /                │  12.1G │   3.0G │   9.1G │  24.5% │ jfs2  │ /dev/hd4      │
│ /usr             │   7.8G │   2.7G │   5.1G │  34.4% │ jfs2  │ /dev/hd2      │
│ /var             │  15.2G │ 343.4M │  14.9G │   2.2% │ jfs2  │ /dev/hd9var   │
│ /tmp             │  40.1G │   7.1G │  33.0G │  17.8% │ jfs2  │ /dev/hd3      │
│ /home            │ 128.0M │ 772.0K │ 127.2M │   0.6% │ jfs2  │ /dev/hd1      │
│ /opt             │  17.1G │   9.7G │   7.4G │  56.9% │ jfs2  │ /dev/hd10opt  │
...

Build

GOOS=aix GOARCH=ppc64 go build

Notes

• Requires Go 1.21+ (official Go, not gccgo)
• Uses golang.org/x/sys/unix which already has full AIX support
• Color output works correctly via termenv (AIX support added in v0.16.0)

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Contributed by LibrePower - Open source tools for IBM Power systems.