Support native ssh-agent on Windows 10 1803

[lusitania]

I understand that KeePassXC only utilises an external SSH agent, such as pageant. With 1803 Windows received native SSH support and an ssh-agent that runs as a service. KeePassXC v.2.3.4 fails to recognise this service.

Expected Behavior

Keys are loaded into into Windows' ssh-agent/OpenSSH Authentication Agent.

Current Behavior

KeePassXC starts with:

No agent running, cannot add identity.

Steps to Reproduce (for bugs)

1. Update to Windows 10 1803 (17134.228)
2. Start-Service ssh-agent as admin
3. Start KeePassXC and have it load SSH keys

Context

Run KeePassXC with Windows' built-in tools.

Debug Info

KeePassXC - Version 2.3.4
Revision: 6fe821c

Libraries:

• Qt 5.11.1
• libgcrypt 1.8.3

Operating system: Windows 10 (10.0)
CPU architecture: x86_64
Kernel: winnt 10.0.17134

Enabled extensions:

• Auto-Type
• Browser Integration
• Legacy Browser Integration (KeePassHTTP)
• SSH Agent
• YubiKey

[hifi]

This already exists as PR #1994.

[lusitania]

duplicates #1984
thanks @hifi