Check automatic variable availability

[franklesniak]

In comparing the Preference Variables documentation for PowerShell 6.x and newer:
https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_preference_variables?view=powershell-6

to the Preference Variables documentation for PowerShell 5.1:
https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_preference_variables?view=powershell-5.1

it seems that a number of Preference Variables were removed/deprecated from PowerShell. I just ran into this problem unexpectedly on a script when testing it on PowerShell 6.x.

To help with this problem, I would like the PSUseCompatibleCommands feature of PSScriptAnalyzer to flag the usage of deprecated Preference Variables and state that they are not compatible with PowerShell 6.0 and newer (on any platform including Windows).

[rjmholt]

Given the name of UseCompatibleCommands, this may or may not be something to put in a new rule. The profiles do record variables though.

I’ll mark this as up-for-grabs, since it’s unlikely I’ll be able to implement it in the medium term. I’d be very happy to review a PR.