[Bug 47899] Review the VM name validation

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=47899

--- Comment #1 from François Gouget  ---
Why were dashes added to the VM name?

Because Windows represents a locale in the form 'lang-COUNTRY': the chain goes
like this: intl.cpl wants dashes -> SetWinLocale wants dashes -> locale
snapshot names contain dashes -> why not name the VM the same.

Plan:
* Don't allow dashes in the VM names.
* Add an UntaintVMName() function.
* Use Unix-style locales everywhere and do the Unix to Windows conversion in
SetWinLocale.
* This impacts LibvirtTool.
* Rename live snapshots to use underscored locale names the next time it's
necessary to recreate them.